Debt - Convertible Bond Hedge, Warrant Transactions (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions		3 Months Ended	12 Months Ended
	Feb. 13, 2014	Mar. 31, 2014	Dec. 31, 2014	Jun. 30, 2016	Feb. 28, 2014	Feb. 14, 2014	Feb. 11, 2014
Convertible Bond Hedge
Common stock covered under convertible bond hedge (in shares)	7.4
Exercise price (in dollars per unit)	$ 27.09
Purchase of convertible bond hedges, net of tax		$ 39.8
Warrant Transactions
Number of shares of common stock called by warrants					7.4
Exercise price (in dollars per share)					$ 34.12
Exercise price above last reported sale price of common stock (as a percent)					70.00%
Sale price of common stock (in dollars per share)							$ 20.07
Proceeds from issuance of warrants			$ 25.7
Convertible 2.5% notes
Debt
Aggregate principal amount of debt issued						$ 200.0
2.5 Percent Convertible Notes
Debt
Aggregate principal amount of debt issued				$ 200.0