Employee Benefit Plans (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011 pension_plan	Dec. 31, 2010	Dec. 31, 2009
Defined Benefit Plan Disclosure [Line Items]
Number of frozen defined benefit pension plans	1
Components of net periodic pension expense
Interest cost	$ 2,409	$ 2,447	$ 2,397
Expected return on plan assets	(2,575)	(2,353)	(1,827)
Amortization of net loss	365	270	679
Total pension expense (benefit)	199	363	1,248
Change in projected benefit obligation:
January 1 projected benefit obligation	44,693	41,627
Interest cost	2,409	2,447	2,397
Benefits paid	(1,641)	(1,568)
Actuarial losses	4,464	2,187
December 31 projected benefit obligation	49,925	44,693	41,627
Change in plan assets:
Fair value at January 1	33,210	30,981
Actual return	(473)	3,261
Employer contributions	2,924	536
Benefits paid	(1,641)	(1,568)
Fair value at December 31	34,020	33,210	30,981
The funded status of the pension plans was as follows:
Funded status (plan assets less than projected benefit obligations)	(15,905)	(11,483)
Unrecognized actuarial loss	15,355	8,208
Net amount recognized	(550)	(3,275)
Unrecognized actuarial losses recorded in accumulated other comprehensive income	(4,515)	1,280
Actuarial assumptions used in determining the funded status information and subsequent net periodic pension cost
Discount rate	4.50%	5.50%	6.00%
Expected long-term weighted average rate of return on plan assets	7.75%	7.75%	7.75%
Weighted-average actual and target asset allocation
Target asset allocations	100.00%
Actual asset allocations	100.00%	100.00%
Expected future benefit plan contributions	2,172
Expected future benefit payments
2012	1,796
2013	1,869
2014	1,977
2015	2,068
2016	2,223
In aggregate during five years thereafter	13,508
Total future benefit payments	23,441
Multi-employer pension plan expense	518	391	525
Defined contribution savings plan expense	6,241	4,949	5,015
Level 1 [Member]
Change in plan assets:
Fair value at December 31	0
Level 2 [Member]
Change in plan assets:
Fair value at December 31	34,020
Level 3 [Member]
Change in plan assets:
Fair value at December 31	0
Equity [Member]
Change in plan assets:
Fair value at December 31	19,109
Weighted-average actual and target asset allocation
Target asset allocations	55.00%
Actual asset allocations	56.00%	57.00%
Equity [Member] | Level 1 [Member]
Change in plan assets:
Fair value at December 31	0
Equity [Member] | Level 2 [Member]
Change in plan assets:
Fair value at December 31	19,109
Equity [Member] | Level 3 [Member]
Change in plan assets:
Fair value at December 31	0
Fixed Income Funds [Member]
Change in plan assets:
Fair value at December 31	14,909
Weighted-average actual and target asset allocation
Target asset allocations	43.00%
Actual asset allocations	44.00%	41.00%
Fixed Income Funds [Member] | Level 1 [Member]
Change in plan assets:
Fair value at December 31	0
Fixed Income Funds [Member] | Level 2 [Member]
Change in plan assets:
Fair value at December 31	12,654
Fixed Income Funds [Member] | Level 3 [Member]
Change in plan assets:
Fair value at December 31	0
Cash and Cash Equivalents [Member]
Change in plan assets:
Fair value at December 31	2
Weighted-average actual and target asset allocation
Target asset allocations	2.00%
Actual asset allocations	0.00%	2.00%
Cash and Cash Equivalents [Member] | Level 1 [Member]
Change in plan assets:
Fair value at December 31	0
Cash and Cash Equivalents [Member] | Level 2 [Member]
Change in plan assets:
Fair value at December 31	2,257
Cash and Cash Equivalents [Member] | Level 3 [Member]
Change in plan assets:
Fair value at December 31	$ 0