Employee Benefit Plans (Details) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Amounts recognized in consolidated balance sheets
Other current liabilities	$ 1,437,000	$ 1,068,000
Other long-term liabilities	75,466,000	66,155,000
Total	76,903,000	67,223,000
Amounts recognized in accumulated other comprehensive loss
Net loss	54,431,000	48,702,000
Prior service cost	0	3,000
Total	54,431,000	48,705,000
Pension plans
Employee Benefits Plans
Expected benefit payments in next fiscal year	8,440,000
Change in benefit obligation
Benefit obligation at beginning of year	160,225,000	147,721,000
Service cost	467,000	457,000	341,000
Interest cost	7,841,000	8,118,000	7,984,000
Actuarial loss	18,745,000	11,533,000
Benefits paid	(8,201,000)	(7,604,000)
Benefit obligation at end of year	179,077,000	160,225,000	147,721,000
Change in plan assets
Fair value of plan assets at beginning of year	93,002,000	97,497,000
Actual return on plan assets	9,952,000	(3,185,000)
Contributions	7,421,000	6,294,000
Benefits paid	(8,201,000)	(7,604,000)
Fair value of plan assets at end of year	102,174,000	93,002,000	97,497,000
Funded status at end of year	(76,903,000)	(67,223,000)
Accumulated benefit obligation in excess of plan assets
Projected benefit obligation	179,077,000	160,255,000
Accumulated benefit obligation	177,442,000	158,097,000
Fair value of plan assets	102,174,000	93,002,000
Net Periodic Benefit Cost (Pre-tax)
Service cost	467,000	457,000	341,000
Interest cost	7,841,000	8,118,000	7,984,000
Expected return on plan assets	(6,733,000)	(7,022,000)	(6,163,000)
Amortization of prior service cost	4,000	49,000	54,000
Recognized actuarial loss	5,999,000	4,519,000	4,081,000
Net periodic benefit cost	7,578,000	6,121,000	6,297,000
Amounts Recognized in Other Comprehensive Loss (Pre-tax)
Net loss	9,548,000	17,222,000	2,681,000
Prior service cost	(4,000)	(49,000)	(54,000)
Total cost recognized in other comprehensive loss	9,544,000	17,173,000	2,627,000
Net cost recognized in net periodic benefit cost and other comprehensive loss	17,122,000	23,294,000	8,924,000
Estimated net loss that will be amortized from accumulated other comprehensive loss into net periodic benefit cost in next fiscal year	6,600,000
Weighted-average assumptions used to determine net periodic benefit cost
Discount rate (as a percent)	5.02%	5.62%	6.20%
Expected return on plan assets (as a percent)	7.25%	7.25%	7.25%
Rate of compensation increase (as a percent)	3.00%	4.00%	4.00%
Weighted-average assumptions used to determine benefit obligations
Discount rate (as a percent)	4.15%	5.02%
Rate of compensation increase (as a percent)	3.00%	4.00%
Period considered for compounded returns	15 years
Frozen pension plan (funded)
Employee Benefits Plans
Contribution by employer in next fiscal year	4,600,000
Change in plan assets
Fair value of plan assets at end of year	102,174,000	93,002,000
Supplemental pension plan (unfunded)
Employee Benefits Plans
Expected benefit payments in next fiscal year	1,400,000
Accumulated benefit obligation in excess of plan assets
Accumulated benefit obligation	$ 26,600,000	$ 23,500,000