United states securities and exchange commission

Table of Contents
BIOGEN INC. AND SUBSIDIARIES
NOTES TO CONSOLIDATED FINANCIAL STATEMENTS — (Continued)
F- 33
Convergence
In connection with our acquisition of Convergence in February 2015 we recorded a contingent consideration 
obligation of $274.5 million. This valuation was based on probability weighted net cash outflow projections of 
$450.0 million, discounted using a rate of 2.0%, which was the estimated cost of debt financing for market 
participants. This liability reflected the revised estimate from the date of acquisition for our initial clinical 
development plans, resulting probabilities of success and the timing of certain milestone payments. For additional 
information on this transaction, please read Note 2, Acquisitions, to these consolidated financial statements. 
As of December 31, 2017 and 2016, the fair value of this contingent consideration obligation was $259.0 
million and $258.9 million, respectively. Our most recent valuation was determined based upon net cash flow 
projections of $400.0 million, probability weighted and discounted using a rate of 2.4%, which is a measure of the 
credit risk associated with settling the liability. 
For 2017 compared to 2016, the net increase in the fair value of this obligation was primarily due to changes 
in the discount rate, partially offset by changes in the expected timing related to the achievement of certain 
remaining developmental milestones. Approximately $147.9 million is reflected as a component of accrued 
expenses and other in our consolidated balance sheets as we expect to make the payment within one year.
Stromedix Inc.
In connection with our acquisition of Stromedix in March 2012 we recorded a contingent consideration 
obligation of $122.2 million. As of December 31, 2017 and 2016, the fair value of this contingent consideration 
obligation was $162.4 million and $133.2 million, respectively. Our most recent valuation was determined based 
upon net cash outflow projections of $344.0 million, probability weighted and discounted using a rate of 2.4%, which 
is a measure of the credit risk associated with settling the liability. 
For 2017 compared to 2016, the net increase in the fair value of this obligation was primarily due to an 
increase in the probability of success related to the achievement of certain remaining developmental milestones, 
partially offset by changes in the discount rate. Approximately $76.7 million is reflected as a component of accrued 
expenses and other in our consolidated balance sheets as we expect to make the payment within one year.
Biogen Idec International Neuroscience GmbH
In connection with our acquisition of BIN in December 2010 we recorded a contingent consideration obligation 
of $81.2 million. As of December 31, 2017 and 2016, the fair value of this contingent consideration obligation was 
$102.2 million and $75.5 million, respectively. Our most recent valuation was determined based upon net cash 
outflow projections of $355.0 million, probability weighted and discounted using a rate of 2.8%, which is a measure 
of the credit risk associated with settling the liability. 
For 2017 compared to 2016, the net increase in the fair value of this obligation was primarily due to an 
increase in the probability of success related to the achievement of certain remaining developmental milestones, 
partially offset by a $6.7 million developmental milestone payment. Approximately $20.0 million is reflected as a 
component of accrued expenses and other in our consolidated balance sheets as we achieved the developmental 
milestone of dosing our first patient in our Phase 2 SPARK study of BIIB054 in Parkinson's disease in January 2018.
Acquired IPR&D
In connection with our acquisition of Convergence, we also allocated $424.6 million of the total purchase price 
to acquired IPR&D, which was capitalized as an intangible asset. The amount allocated to acquired IPR&D was based 
on significant inputs not observable in the market and thus represented a Level 3 fair value measurement. These 
assets will be tested for impairment annually until commercialization, after which time the IPR&D will be amortized 
over its estimated useful life using the economic consumption method. For additional information on this 
transaction, please read Note 2, Acquisitions, to these consolidated financial statements.

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Table of Contents
BIOGEN INC. AND SUBSIDIARIES
NOTES TO CONSOLIDATED FINANCIAL STATEMENTS — (Continued)
F- 34
9.    Financial Instruments
The following table summarizes our financial assets with maturities of less than 90 days from the date of 
purchase included in cash and cash equivalents in our consolidated balance sheets:
 
As of December 31,
(In millions)
2017
2016
Commercial paper
$
30.5
$
31.0
Overnight reverse repurchase agreements
3.6
—
Money market funds
948.0
741.7
Short-term debt securities
247.3
1,266.9
Total
$
1,229.4
$
2,039.6
The carrying values of our commercial paper, including accrued interest, overnight reverse repurchase 
agreements, money market funds and our short-term debt securities approximate fair value due to their short-term 
maturities. 
The following tables summarize our marketable debt and equity securities, classified as available for sale:
As of December 31, 2017 (In millions)
Fair
Value
Gross
Unrealized
Gains
Gross
Unrealized
Losses
Amortized
Cost
Corporate debt securities
Current
$
1,039.3 $
— $
(0.2) $
1,039.5
Non-current
1,570.5
0.9
—
1,569.6
Government securities
Current
1,075.1
0.1
(0.7)
1,075.7
Non-current
844.2
0.2
(1.1)
845.1
Mortgage and other asset backed securities
Current
0.8
—
—
0.8
Non-current
642.6
1.1
(0.8)
642.3
Total marketable debt securities
$
5,172.5 $
2.3 $
(2.8) $
5,173.0
Marketable equity securities, non-current
$
11.8 $
1.8 $
(4.4) $
14.4
As of December 31, 2016 (In millions)
Fair
Value
Gross
Unrealized
Gains
Gross
Unrealized
Losses
Amortized
Cost
Corporate debt securities
Current
$
1,408.6 $
0.2 $
(0.6) $
1,409.0
Non-current
1,255.2
1.2
(4.7)
1,258.7
Government securities
Current
1,156.0
0.2
(0.3)
1,156.1
Non-current
1,016.5
0.5
(3.4)
1,019.4
Mortgage and other asset backed securities
Current
4.0
—
—
4.0
Non-current
557.7
0.8
(2.2)
559.1
Total marketable debt securities
$
5,398.0 $
2.9 $
(11.2) $
5,406.3
Marketable equity securities, non-current
$
24.9 $
0.7 $
(9.3) $
33.5

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