Shareholders' Equity-Common Stock Rollforward (Details) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 01, 2015	Sep. 26, 2015	May. 01, 2015	May. 31, 2014
Repurchases of common stock	2,617,991	8,474,574
Preferred Stock, Shares Authorized		2,000,000
Stock Repurchase Program, Authorized Amount	$ 400,000		$ 400,000		$ 200,000	$ 400,000	$ 200,000	$ 200,000
Treasury Stock, Value, Acquired, Cost Method	$ 149,631	$ 480,217
Common Stock Issued [Member]
Common stock outstanding, Beginning balance		125,424	125,424	125,424
Shares issued for stock-based compensation awards		0	0	0
Repurchases of common stock		0	0	0
Common stock outstanding, Ending balance	125,424	125,424	125,424	125,424
Treasury Stock [Member]
Common stock outstanding, Beginning balance		29,529	25,488	19,423
Shares issued for stock-based compensation awards		(1,155)	(1,506)	(2,772)
Repurchases of common stock		6,127	5,547	8,837
Common stock outstanding, Ending balance	29,529	34,501	29,529	25,488
Common Stock at Par Value [Member]
Common stock outstanding, Beginning balance		95,895	99,936	106,001
Shares issued for stock-based compensation awards		1,155	(1,506)	2,772
Repurchases of common stock		(6,127)	(5,547)	(8,837)
Common stock outstanding, Ending balance	95,895	90,923	95,895	99,936