Shareholders' Equity - Shares Repurchased (Details) - USD ($)	1 Months Ended	3 Months Ended					4 Months Ended	12 Months Ended	52 Months Ended
	May 04, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	May 04, 2017	Dec. 31, 2016	May 04, 2017	Feb. 24, 2016
Equity, Class of Treasury Stock [Line Items]
Repurchases of common stock		$ 216,000,000				$ 75,000,000
Common Stock [Member]
Equity, Class of Treasury Stock [Line Items]
Shares repurchased (in shares)		5,430,041	3,300,617	2,050,229	2,331,474	3,038,928		10,721,248
Repurchases of common stock		$ 216,000,000	$ 116,000,000	$ 55,000,000	$ 60,000,000	$ 75,000,000		$ 306,000,000
Treasury Stock Acquired, Average Cost Per Share		$ 39.83	$ 35.09	$ 26.83	$ 25.73	$ 24.69		$ 28.53
Authorized repurchase amount										$ 300,000,000
Subsequent Event [Member] | Common Stock [Member]
Equity, Class of Treasury Stock [Line Items]
Shares repurchased (in shares)	1,377,928						6,807,969		75,451,176
Repurchases of common stock	$ 53,000,000						$ 269,000,000		$ 1,984,000,000
Treasury Stock Acquired, Average Cost Per Share	$ 38.13						$ 39.49		$ 26.29
Remaining capacity of shares repurchase program	$ 280,000,000						$ 280,000,000		$ 280,000,000
Chief Executive Officer [Member]
Equity, Class of Treasury Stock [Line Items]
Number of shares authorized to be repurchased (in shares)		297,131
Deferred compensation equity, shares to be paid in the future (in shares)		297,131
Deferred equity compensation (in shares)		297,131
General Counsel [Member]
Equity, Class of Treasury Stock [Line Items]
Number of shares authorized to be repurchased (in shares)		23,062
Deferred compensation equity, shares to be paid in the future (in shares)		23,062
Deferred equity compensation (in shares)		23,062