Shareholders' Deficit (Details) - USD ($) $ / shares in Units, $ in Millions			3 Months Ended		6 Months Ended
	Apr. 24, 2015	Feb. 20, 2015	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Dividends
Cash dividends declared per common share (in dollars per share)	$ 0.25	$ 0.25	$ 0.25	$ 0.00	$ 0.50	$ 0.00
Dividends paid			$ 29.2		$ 58.0
Common Stock
Shareholders' Deficit
Awards exercised (in shares)					111,156	79,000
Weighted-average exercise price of awards exercised (in dollars per share)					$ 13.75	$ 12.89
Total cash proceeds					$ 1.5	$ 1.0
Governance agreement | GSK | Common Stock
Shareholders' Deficit
Common stock purchased (in shares)					178,253
Aggregate purchase price of common stock					$ 3.0