Income Tax Expense (Details 4) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Unrecognized Tax Benefits
Unrecognized tax benefit, if recognized, would have an impact on effective tax rate	$ 1,303
Interest and penalties related to unrecognized tax benefits, recognized in income tax expense	67	102	(1,206)
Payment of interest and penalties accrued	440	484
Activity for unrecognized tax benefits
Balance at beginning of period	1,760	6,612	18,250
Tax positions related to current year additions	162
Additions for tax positions of prior years	165	211
Tax positions related to prior years reductions			(1,114)
Reductions due to lapse of statute of limitations on tax positions		(5,020)	(33)
Settlements	(211)	(43)	(10,491)
Balance at end of period	$ 1,876	$ 1,760	$ 6,612