XML 183 R21.htm IDEA: XBRL DOCUMENT
v3.19.3.a.u2

Earnings per Share | 12 Months Ended
--- | ---
Dec. 31, 2019
Earnings Per Share [Abstract] |
Earnings per Share | Earnings per Share Basic and diluted earnings per share are calculated as follows:
| For the Years Ended December 31,
(In millions) | 2019 |  | 2018 |  | 2017
Numerator: |  |  |  |  |
Net income attributable to Biogen Inc. | $ | 5,888.5 |  |  | $ | 4,430.7 |  |  | $ | 2,539.1 |
Denominator: |  |  |  |  |
Weighted average number of common shares outstanding | 187.1 |  |  | 204.9 |  |  | 212.6 |
Effect of dilutive securities: |  |  |  |  |
Stock options and employee stock purchase plan | — |  |  | — |  |  | 0.1 |
Time-vested restricted stock units | 0.2 |  |  | 0.3 |  |  | 0.2 |
Market stock units | 0.1 |  |  | 0.1 |  |  | 0.1 |
Performance stock units settled in stock | — |  |  | — |  |  | — |
Dilutive potential common shares | 0.3 |  |  | 0.4 |  |  | 0.4 |
Shares used in calculating diluted earnings per share | 187.4 |  |  | 205.3 |  |  | 213.0 |
Amounts excluded from the calculation of net income per diluted share because their effects were anti-dilutive were insignificant. Earnings per share for the years ended December 31, 2019, 2018 and 2017, reflects, on a weighted average basis, the repurchase of approximately 23.6 million shares, 14.8 million shares and 3.7 million shares of our common stock, respectively, under our March 2019, 2018 and 2016 Share Repurchase Programs.

X
- References No definition available. + Details
Name: | us-gaap_EarningsPerShareAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition The entire disclosure for earnings per share. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 260 -URI http://asc.fasb.org/topic&trid=2144383 + Details
Name: | us-gaap_EarningsPerShareTextBlock
Namespace Prefix: | us-gaap_
Data Type: | nonnum:textBlockItemType
Balance Type: | na
Period Type: | duration