Income Tax Expense (Details 4) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Unrecognized Tax Benefits
Unrecognized tax benefit, if recognized, would have an impact on effective tax rate	$ 1,272
Interest and penalties related to unrecognized tax benefits, recognized in income tax expense	44	67	102
Payment of interest and penalties accrued	396	440
Activity for unrecognized tax benefits
Balance at beginning of period	1,876	1,760	6,612
Tax positions related to current year additions	41	162
Additions for tax positions of prior years	89	165	211
Tax positions related to prior years reductions			0
Reductions due to lapse of statute of limitations on tax positions		0	(5,020)
Settlements	(225)	(211)	(43)
Balance at end of period	$ 1,781	$ 1,876	$ 1,760