Shareholders' Equity - Shares Repurchased (Details) - USD ($)	1 Months Ended	12 Months Ended			37 Months Ended
	Feb. 09, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Feb. 09, 2016	Feb. 24, 2016
Equity, Class of Treasury Stock [Line Items]
Repurchases of common stock		$ (555,000,000)	$ (590,000,000)	$ (264,000,000)
Common Stock [Member]
Equity, Class of Treasury Stock [Line Items]
Authorized repurchase amount		$ 55,000,000
Shares repurchased		20,995,419	24,413,781	12,512,759
Repurchases of common stock		$ (555,000,000)	$ (590,000,000)	$ (264,000,000)
Average price paid (in dollars per share)		$ 26.43	$ 24.17	$ 21.12
Affiliated Entity [Member] | Common Stock [Member]
Equity, Class of Treasury Stock [Line Items]
Shares repurchased				5,000,000
Repurchases of common stock				$ (109,700,000)
Subsequent Event [Member] | Common Stock [Member]
Equity, Class of Treasury Stock [Line Items]
Authorized repurchase amount						$ 250,000,000
Shares repurchased	2,258,602				60,180,561
Repurchases of common stock	$ (55,000,000)				$ (1,464,000,000)
Average price paid (in dollars per share)	$ 24.37				$ 24.33