United states securities and exchange commission

Table of Contents
BIOGEN INC. AND SUBSIDIARIES
NOTES TO CONSOLIDATED FINANCIAL STATEMENTS — (Continued)
F- 41
Common Stock
The following table describes the number of shares authorized, issued and outstanding of our common stock 
as of December 31, 2017 and 2016:
 
As of December 31, 2017
As of December 31, 2016
(In millions)
Authorized
Issued
Outstanding
Authorized
Issued
Outstanding
Common stock
1,000.0
235.3
211.5
1,000.0
238.5
215.9
Share Repurchases
In July 2016 our Board of Directors authorized a program to repurchase up to $5.0 billion of our common stock 
(2016 Share Repurchase Program). This authorization does not have an expiration date. All share repurchases under 
this authorization will be retired. Under this authorization, we repurchased and retired 3.7 million and 3.3 million 
shares of common stock during the years ended December 31, 2017 and 2016, respectively, at a cost of $1.0 
billion for each year. As of December 31, 2017, approximately $3.0 billion remains available for share repurchases 
under this authorization.
In May 2015 our Board of Directors authorized a program to repurchase up to $5.0 billion of our common stock 
(2015 Share Repurchase Program). All shares repurchased under this authorization were retired. Our 2015 Share 
Repurchase Program was completed as of December 31, 2015. Under this authorization, we repurchased and retired 
approximately 16.8 million shares of common stock at a cost of $5.0 billion during the year ended December 31, 
2015.
In February 2011 our Board of Directors authorized a program to repurchase up to 20.0 million shares of our 
common stock (2011 Share Repurchase Program). Shares repurchased under this authorization were principally 
used to offset common stock issuances under our share-based compensation programs. Our 2011 Share 
Repurchase Program was completed as of March 31, 2017. Under this authorization, we repurchased 1.2 million 
shares of common stock at a cost of $365.4 million during the year ended December 31, 2017. We did not 
repurchase any shares of common stock under this authorization during the years ended December 31, 2016 and 
2015. 
14.    Accumulated Other Comprehensive Income (Loss)
The following table summarizes the changes in accumulated other comprehensive income (loss), net of tax by 
component:
(In millions)
Unrealized Gains
(Losses) on
Securities
Available for Sale,
net of tax
Unrealized Gains
(Losses) on Cash
Flow Hedges, net
of tax
Unfunded Status
of Postretirement
Benefit Plans, net
of tax
Translation
Adjustments
Total
Balance, December 31, 2016
$
(10.8) $
57.8 $
(32.7) $
(334.2) $
(319.9)
Other comprehensive
income (loss) before
reclassifications
(3.5)
(193.8)
(4.1)
158.7
(42.7)
Amounts reclassified from
accumulated other
comprehensive income
(loss)
12.7
31.5
—
—
44.2
Net current period other
comprehensive income (loss)
9.2
(162.3)
(4.1)
158.7
1.5
Balance, December 31, 2017
$
(1.6) $
(104.5) $
(36.8) $
(175.5) $
(318.4)

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Table of Contents
BIOGEN INC. AND SUBSIDIARIES
NOTES TO CONSOLIDATED FINANCIAL STATEMENTS — (Continued)
F- 42
(In millions)
Unrealized Gains
(Losses) on
Securities
Available for Sale,
net of tax
Unrealized Gains
(Losses) on Cash
Flow Hedges, net
of tax
Unfunded Status
of Postretirement
Benefit Plans, net
of tax
Translation
Adjustments
Total
Balance, December 31, 2015
$
(0.8) $
10.2 $
(37.8) $
(195.6) $
(224.0)
Other comprehensive
income (loss) before
reclassifications
(10.6)
51.6
5.1
(138.6)
(92.5)
Amounts reclassified from
accumulated other
comprehensive income
(loss)
0.6
(4.0)
—
—
(3.4)
Net current period other
comprehensive income (loss)
(10.0)
47.6
5.1
(138.6)
(95.9)
Balance, December 31, 2016
$
(10.8) $
57.8 $
(32.7) $
(334.2) $
(319.9)
(In millions)
Unrealized Gains
(Losses) on
Securities
Available for Sale,
net of tax
Unrealized Gains
(Losses) on Cash
Flow Hedges, net
of tax
Unfunded Status
of Postretirement
Benefit Plans, net
of tax
Translation
Adjustments
Total
Balance, December 31, 2014
$
(0.4) $
71.7 $
(31.6) $
(99.2) $
(59.5)
Other comprehensive
income (loss) before
reclassifications
(1.7)
110.8
(6.2)
(96.4)
6.5
Amounts reclassified from
accumulated other
comprehensive income
(loss)
1.3
(172.3)
—
—
(171.0)
Net current period other
comprehensive income (loss)
(0.4)
(61.5)
(6.2)
(96.4)
(164.5)
Balance, December 31, 2015
$
(0.8) $
10.2 $
(37.8) $
(195.6) $
(224.0)
The following table summarizes the amounts reclassified from accumulated other comprehensive income:
(In millions)
Income Statement Location
Amounts Reclassified from
Accumulated Other Comprehensive Income
For the Years Ended December 31,
2017
2016
2015
Gains (losses) on securities
available for sale
Other income (expense)
$
(19.5)
$
(0.9) $
(2.0)
Income tax benefit
(expense)
6.8
0.3
0.7
Gains (losses) on cash flow
hedges
Revenues
(32.5)
5.3
173.2
Operating expenses
0.6
(1.5)
—
Other income (expense)
0.3
0.2
(0.1)
Income tax benefit
(expense)
0.1
—
(0.8)
Total reclassifications, net of
tax
$
(44.2)
$
3.4 $
171.0

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