Debt - Convertible Bond Hedge, Warrant Transactions (Details) - USD ($) $ / shares in Units, shares in Millions	1 Months Ended	12 Months Ended
	Feb. 28, 2014	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Feb. 11, 2014
Debt Instrument [Line Items]
Common stock covered under convertible bond hedge (shares)	7.4
Exercise price (USD per share)	$ 27.09
Purchase of convertible bond hedges, net of tax				$ 39,800,000
Number of shares of common stock called by warrants (shares)	7.4
Initial exercise price (USD per share)	$ 34.12
Exercise price above last reported sale price of common stock (percent)	70.00%
Sale price of common stock (USD per share)					$ 20.07
Payment of debt issuance costs		$ 0	$ 0	$ 25,620,000
Convertible 2.5% notes
Debt Instrument [Line Items]
Principal amount of debt at time of issuance	$ 200,000,000