Shareholders' Equity Repurchase Program (Details) - USD ($)	Dec. 31, 2016	Nov. 04, 2016	Jan. 06, 2016	Dec. 31, 2015	Nov. 11, 2015	Aug. 11, 2015	Jul. 20, 2015	Jul. 21, 2014	Jun. 30, 2014
Accelerated Share Repurchases [Line Items]
Treasury Stock, Shares	8,003,000		363,209	7,430,000		3,059,629
Treasury Stock, Value	$ 257,683,000			$ 238,775,000
Stock Repurchase Program, Number of Shares Authorized to be Repurchased						50,000,000
Stock Repurchase Program, Authorized Amount	$ 100,000,000		$ 375,000,000				$ 400,000,000		$ 25,000,000
Maximum
Accelerated Share Repurchases [Line Items]
Stock Repurchase Program, Authorized Amount							$ 450,000,000	$ 200,000,000
Fourth Accelerated Share Repurchase Agreement [Member] [Member]
Accelerated Share Repurchases [Line Items]
Treasury Stock, Shares	209,618
Treasury Stock, Value		$ 0
Stock Repurchase Program, Authorized Amount		$ 0
Third Accelerated Share Repurchase Agreement [Member]
Accelerated Share Repurchases [Line Items]
Treasury Stock, Shares					1,985,981
Treasury Stock, Value					$ 63,750,000