Employee Benefit Plans (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Defined Benefit Plan, Amounts Recognized in Balance Sheet [Abstract]
Noncurrent liabilities	$ (140,623)	$ (66,335)
Pension Plans, Defined Benefit [Member]
Defined Benefit Plan, Change in Benefit Obligation [Rollforward]
Projected benefit obligation at beginning of year	346,464	324,554
Service cost	6,782	6,196	6,489
Interest cost	18,087	17,740	18,082
Actuarial loss	58,208	11,766
Plan amendments	0	1,704
Employee contributions	0	0
Benefits paid	(16,394)	(15,496)
Projected benefit obligation at end of year	413,147	346,464	324,554
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at beginning of year	302,464	231,686
Actual return on plan assets	8,977	35,636
Employer contributions	1,552	51,510
Employee contributions	0	0
Benefits paid	(16,394)	(15,496)
Other expense	(944)	(872)
Fair value of plan assets at end of year	295,655	302,464	231,686
Defined Benefit Plan, Funded Status of Plan [Abstract]
Funded status at end of year, net accrued benefit cost	(117,492)	(44,000)
Defined Benefit Plan, Amounts Recognized in Balance Sheet [Abstract]
Noncurrent assets	0	3,032
Current liabilities	(1,626)	(1,475)
Noncurrent liabilities	(115,866)	(45,557)
Net amount recognized	(117,492)	(44,000)
Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plan, Change in Benefit Obligation [Rollforward]
Projected benefit obligation at beginning of year	21,158	21,361
Service cost	673	587	482
Interest cost	972	1,029	1,144
Actuarial loss	3,934	965
Plan amendments	(631)	0
Employee contributions	1,609	1,042
Benefits paid	(2,882)	(3,826)
Projected benefit obligation at end of year	24,833	21,158	21,361
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at beginning of year	0	0
Actual return on plan assets	0	0
Employer contributions	1,273	2,784
Employee contributions	1,609	1,042
Benefits paid	(2,882)	(3,826)
Other expense	0	0
Fair value of plan assets at end of year	0	0	0
Defined Benefit Plan, Funded Status of Plan [Abstract]
Funded status at end of year, net accrued benefit cost	(24,833)	(21,158)
Defined Benefit Plan, Amounts Recognized in Balance Sheet [Abstract]
Noncurrent assets	0	0
Current liabilities	(1,262)	(1,566)
Noncurrent liabilities	(23,571)	(19,592)
Net amount recognized	$ (24,833)	$ (21,158)