Common Stock (Details) (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Stock issued during period, treasury, shares	0	0
Common stock repurchases, value	$ 34,066	$ 28,100	$ 314
Treasury Stock [Member]
Stock Issued During Period, Shares, Employee Benefit Plan			737,463
Stock issued during period, treasury, shares			1,154,265
Common stock repurchases, shares	1,509,000	1,484,000	21,000
Common stock repurchases, value	$ 34,066	$ 28,100	$ 314
Common Stock [Member]
Employee stock plans, shares	2,076,000	544,000	744,000