Shareholders' Equity - Shares Repurchased (Details) - USD ($)	2 Months Ended	12 Months Ended
	Feb. 23, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Feb. 22, 2017
Equity, Class of Treasury Stock [Line Items]
Deferred equity compensation (in shares)		320,193	320,193
Total payments		$ 306,000,000	$ 555,000,000	$ 590,000,000
Common Stock [Member]
Equity, Class of Treasury Stock [Line Items]
Number of Shares Repurchased (in shares)		10,721,248	20,995,419	24,413,781
Total payments		$ 306,000,000	$ 555,000,000	$ 590,000,000
Average price paid (in dollars per share)		$ 28.53	$ 26.43	$ 24.17
Subsequent Event [Member] | Common Stock [Member]
Equity, Class of Treasury Stock [Line Items]
Authorized repurchase amount					$ 300,000,000
Stock Repurchase Program, Remaining Number of Shares Authorized to be Repurchased	$ 407,000,000
Number of Shares Repurchased (in shares)	3,591,369
Total payments	$ 142,000,000
Average price paid (in dollars per share)	$ 39.65