Summary of Significant Accounting Policies (Effects of Adoption of Topic 606 - Unaudited Consolidated Statements of Operations) (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Product sales	$ 3,637.1	$ 3,412.3
Royalties and other revenues	128.6	160.0
Net income	$ 550.6	$ 375.0
Net income per share applicable to common shareholders - basic (in usd per share)	$ 0.61	$ 0.41
Net income per share applicable to common shareholders - diluted (in usd per share)	$ 0.60	$ 0.41
Before Adoption of Topic 606 | ASU 2014-09
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Product sales	$ 3,642.5
Royalties and other revenues	151.4
Net income	$ 572.4
Net income per share applicable to common shareholders - basic (in usd per share)	$ 0.63
Net income per share applicable to common shareholders - diluted (in usd per share)	$ 0.63
Effect of change | ASU 2014-09
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Product sales	$ (5.4)
Royalties and other revenues	(22.8)
Net income	$ (21.8)
Net income per share applicable to common shareholders - basic (in usd per share)	$ (0.02)
Net income per share applicable to common shareholders - diluted (in usd per share)	$ (0.03)