United states securities and exchange commission

Table of Contents
BIOGEN INC. AND SUBSIDIARIES
NOTES TO CONSOLIDATED FINANCIAL STATEMENTS — (Continued)
F- 13
Other Assets and Liabilities
The carrying amounts reflected in our consolidated balance sheets for current accounts receivable, due from 
anti-CD20 therapeutic programs, other current assets, accounts payable and accrued expenses and other, 
approximate fair value due to their short-term maturities.
Cash and Cash Equivalents
We consider only those investments which are highly liquid, readily convertible to cash and that mature within 
three months from date of purchase to be cash equivalents. As of December 31, 2017 and 2016, cash equivalents 
were comprised of money market funds and commercial paper, overnight reverse repurchase agreements and other 
debt securities with maturities less than 90 days from the date of purchase.
Accounts Receivable
The majority of our accounts receivable arise from product sales and primarily represent amounts due from our 
wholesale distributors, public hospitals and other government entities. We monitor the financial performance and 
creditworthiness of our customers so that we can properly assess and respond to changes in their credit profile. We 
provide reserves against trade receivables for estimated losses that may result from a customer’s inability to pay. 
Amounts determined to be uncollectible are charged or written-off against the reserve. To date, our historical 
reserves and write-offs of accounts receivable have not been significant.
In countries where we have experienced a pattern of payments extending beyond our contractual payment term 
and we expect to collect receivables greater than one year from the time of sale, we have discounted our receivables 
and reduced related revenues over the period of time that we estimate those amounts will be paid using the 
country’s market-based borrowing rate for such period. The related receivables are classified at the time of sale as 
non-current assets. We accrete interest income on these receivables, which is recognized as a component of other 
income (expense), net in our consolidated statements of income.
Concentration of Credit Risk
Financial instruments that potentially subject us to concentrations of credit risk include cash and cash 
equivalents, investments, derivatives and accounts receivable. We attempt to minimize the risks related to cash and 
cash equivalents and investments by investing in a broad and diverse range of financial instruments as previously 
defined by us. We have established guidelines related to credit ratings and maturities intended to safeguard principal 
balances and maintain liquidity. Our investment portfolio is maintained in accordance with our investment policy, 
which defines allowable investments, specifies credit quality standards and limits the credit exposure of any single 
issuer. We minimize credit risk resulting from derivative instruments by choosing only highly rated financial 
institutions as counterparties.
Concentrations of credit risk with respect to receivables, which are typically unsecured, are somewhat mitigated 
due to the wide variety of customers and markets using our products, as well as their dispersion across many 
different geographic areas. The majority of our accounts receivable arise from product sales in the U.S. and Europe 
and have standard payment terms that generally require payment within 30 to 90 days. We monitor the financial 
performance and creditworthiness of our customers so that we can properly assess and respond to changes in their 
credit profile. We continue to monitor these conditions and assess their possible impact on our business. 
As of December 31, 2017 and 2016, two wholesale distributors individually accounted for approximately 26.5% 
and 19.0%, and 37.2% and 19.2%, of accounts receivable, net, respectively. 
Marketable Securities and Other Investments
Marketable Debt Securities
Available-for-sale debt securities are recorded at fair market value and unrealized gains and losses are included 
in accumulated other comprehensive income (loss) in equity, net of related tax effects, unless the security has 
experienced a credit loss, we have determined that we have the intent to sell the security or we have determined that 
it is more likely than not that we will have to sell the security before its expected recovery. Realized gains and losses 
are reported in other income (expense), net, on a specific identification basis.

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Table of Contents
BIOGEN INC. AND SUBSIDIARIES
NOTES TO CONSOLIDATED FINANCIAL STATEMENTS — (Continued)
F- 14
Marketable Equity Securities
Our marketable equity securities represent investments in publicly traded equity securities and are included in 
investments and other assets in our consolidated balance sheets. When assessing whether a decline in the fair 
value of a marketable equity security is other-than-temporary, we consider the fair market value of the security, the 
duration of the security’s decline and prospects for the underlying business, including favorable or adverse clinical 
trial results, new product initiatives and new collaborative agreements with the companies in which we have invested.
Non-Marketable Equity Securities
We also invest in equity securities of companies whose securities are not publicly traded and where fair value 
is not readily available. These investments are recorded using either the cost method or the equity method of 
accounting, depending on our ownership percentage and other factors that suggest we have significant influence. We 
monitor these investments to evaluate whether any decline in their value has occurred that would be other-than-
temporary, based on the implied value of recent company financings, public market prices of comparable companies 
and general market conditions and are included in investments and other assets in our consolidated balance sheets.
Evaluating Investments for Other-than-Temporary Impairments
We conduct periodic reviews to identify and evaluate each investment that has an unrealized loss, in 
accordance with the meaning of other-than-temporary impairment and its application to certain investments. An 
unrealized loss exists when the current fair value of an individual security is less than its amortized cost basis. 
Unrealized losses on available-for-sale securities that are determined to be temporary, and not related to credit loss, 
are recorded, net of tax, in accumulated other comprehensive income.
For available-for-sale debt securities with unrealized losses, management performs an analysis to assess 
whether we intend to sell or whether we would more likely than not be required to sell the security before the 
expected recovery of the amortized cost basis. Where we intend to sell a security, or may be required to do so, the 
security’s decline in fair value is deemed to be other-than-temporary and the full amount of the unrealized loss is 
reflected in earnings as an impairment loss.
Regardless of our intent to sell a security, we perform additional analysis on all securities with unrealized 
losses to evaluate losses associated with the creditworthiness of the security. Credit losses are identified where we 
do not expect to receive cash flows sufficient to recover the amortized cost basis of a security.
For equity securities, when assessing whether a decline in value is other-than-temporary, we consider the fair 
market value of the security, the duration of the security’s decline and the financial condition of the issuer. We then 
consider our intent and ability to hold the equity security for a period of time sufficient to recover our carrying value. 
Where we have determined that we lack the intent and ability to hold an equity security to its expected recovery, the 
security’s decline in fair value is deemed to be other-than-temporary and is reflected in earnings as an impairment 
loss.
Equity Method of Accounting
In circumstances where we have the ability to exercise significant influence over the operating and financial 
policies of a company in which we have an investment, we utilize the equity method of accounting for recording 
investment activity. In assessing whether we exercise significant influence, we consider the nature and magnitude of 
our investment, the voting and protective rights we hold, any participation in the governance of the other company 
and other relevant factors such as the presence of a collaborative or other business relationship. Under the equity 
method of accounting, we record in our results of operations our share of income or loss of the other company. If our 
share of losses exceeds the carrying value of our investment, we will suspend recognizing additional losses and will 
continue to do so unless we commit to providing additional funding. 
Inventory
Inventories are stated at the lower of cost or market with cost based on the first-in, first-out method. We 
classify our inventory costs as long-term when we expect to utilize the inventory beyond our normal operating cycle 
and include these costs in investments and other assets in our consolidated balance sheets. Inventory that can be 
used in either the production of clinical or commercial products is expensed as research and development costs 
when identified for use in a clinical manufacturing campaign.

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