Employee Benefit Plans (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Defined Benefit Pension Plan [Member]
Change in benefit obligations:
Beginning projected benefit obligation	$ 48,018	$ 42,829
Service cost	1,516	1,400	1,647
Interest cost	2,607	2,493	2,605
Actuarial (gain)/loss	7,239	2,510
Benefits paid	(1,273)	(1,214)
Ending projected benefit obligation	58,107	48,018	42,829
Change in plan assets:
Beginning fair value	35,755	31,455
Actual return	(1,516)	4,014
Company contribution	1,500	1,500
Benefits paid	(1,273)	(1,214)
Ending fair value	34,466	35,755	31,455
Funded status of the plan	(23,641)	(12,263)
Supplementary Pension Plan [Member]
Change in benefit obligations:
Beginning projected benefit obligation	9,220	9,029
Service cost	196	320	216
Interest cost	485	533	450
Actuarial (gain)/loss	2,043	(516)
Benefits paid	(376)	(146)
Ending projected benefit obligation	11,568	9,220	9,029
Change in plan assets:
Beginning fair value	0	0
Actual return	0	0
Company contribution	376	146
Benefits paid	(376)	(146)
Ending fair value	0	0	0
Funded status of the plan	$ (11,568)	$ (9,220)