Capital Stock - Narrative (Details) - USD ($) $ / shares in Units, $ in Thousands				12 Months Ended
	Mar. 02, 2016	Feb. 26, 2016	Feb. 22, 2016	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	May 01, 2014
Incentive Plans
Issuance of common stock (in shares)	6,600,000.0		44,000,000
Share price (in usd per share)			$ 19.675
Sale of common stock, net	$ 129,900	$ 865,700		$ 995,279	$ 0	$ 0
Number of shares repurchased				0	0	4,300,000
Cost of shares repurchased						$ 138,852
Cumulative number of shares repurchased under a share repurchase program				29,900,000
Treasury stock, number of shares authorized to be repurchased				40,000,000.0
Treasury stock, cumulative shares retired				20,000,000
Cumulative cost of shares repurchased under a share repurchase program				$ 388,400
Treasury stock reissued				0
Shares held as treasury stock (in shares)				9,892,680	9,892,680
2014 Incentive Plan
Incentive Plans
Number of shares reserved for issuance							18,000,000
Number of shares available for issuance				16,000,000
2014 Incentive Plan | Stock options | Maximum
Incentive Plans
Number of shares reserved for issuance							10,000,000