Shareholders' Deficit (Details) - USD ($) $ / shares in Units, $ in Millions				3 Months Ended		9 Months Ended
	Jul. 24, 2015	Apr. 24, 2015	Feb. 20, 2015	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Dividends
Cash dividends declared per common share (in dollars per share)	$ 0.25	$ 0.25	$ 0.25	$ 0.25	$ 0.25	$ 0.75	$ 0.25
Dividends paid				$ 29.1		$ 87.1
Common Stock
Shareholders' Deficit
Awards exercised (in shares)						111,156	1,127,000
Weighted-average exercise price of awards exercised (in dollars per share)						$ 13.75	$ 14.09
Total cash proceeds						$ 1.5	$ 15.9
Governance agreement | GSK | Common Stock
Shareholders' Deficit
Common stock purchased (in shares)						424,081
Aggregate purchase price of common stock						$ 6.5