Comprehensive Income (details) (USD $) In Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010	Dec. 31, 2010
Accumulated Other Comprehensive Income Loss Net Of Tax Abstract
Accumulated other comprehensive income (loss)	$ (6,312)	$ (5,772)	$ (6,312)	$ (5,772)	$ (6,604)
Other Comprehensive Income Loss Net Of Tax Portion Attributable To Parent Abstract
Net income	2,193	6,888	42,966	50,496
Amortization of employee benefit plan liability, net of tax	146	98	292	196
Total Comprehensive Income	$ 2,339	$ 6,986	$ 43,258	$ 50,692