Shareholders' Equity (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Repurchases of common stock	2,922,822
Preferred Stock, Shares Authorized	2,000,000
Stock Repurchase Program, Amount Authorized	200,000
Treasury Stock, Value, Acquired, Cost Method	102,285
Common Stock Issued [Member]
Common stock outstanding, Beginning balance	125,382	125,337	125,287
Shares issued for stock-based compensation awards	42	45	50
Repurchases of common stock	0	0	0
Common stock outstanding, Ending balance	125,424	125,382	125,337
Treasury Stock [Member]
Common stock outstanding, Beginning balance	13,568	10,690	5,459
Shares issued for stock-based compensation awards	(1,326)	(2,662)	(1,070)
Repurchases of common stock	7,181	5,540	6,301
Common stock outstanding, Ending balance	19,423	13,568	10,690
Common Stock at Par Value [Member]
Common stock outstanding, Beginning balance	111,814	114,647	119,828
Shares issued for stock-based compensation awards	1,368	2,707	1,120
Repurchases of common stock	(7,181)	(5,540)	(6,301)
Common stock outstanding, Ending balance	106,001	111,814	114,647