Employee Benefit Plans Employee Benefit Plans (Schedule of Defined Benefit Plans Disclosures) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Defined Benefit Plan Disclosure [Line Items]
Accumulated gain (loss)	$ 4,700	$ 5,500
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit Obligations at January 1	54,184
Curtailments	(1,770)
Benefit Obligations at December 31			17,412
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Value of Plan Assets at January 1	285,074
Value of Plan Assets at December 31	322,874
Pension Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Accrued benefit cost	(68,020)	(48,877)
Prior service cost (credit)	1,890	1,736
Accumulated gain (loss)	(68,915)	(68,302)
Total not yet recognized as a component of net periodic benefit cost	(67,025)	(66,566)
Current liability	(390)	(633)
Noncurrent liability	(67,630)	(48,244)
Pension and Other Postretirement Defined Benefit Plans, Liabilities	(68,020)	(48,877)
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit Obligations at January 1	333,951	297,707
Service cost	27,466	16,490	15,870
Interest cost	15,668	16,253	15,822
Plan Amendments		(3,235)
Benefits Paid	(23,624)	(18,848)
Curtailments	(687)
Acquisition of ICG
Other-primary actuarial loss (gain)	38,120	25,584
Benefit Obligations at December 31	390,894	333,951	297,707
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Value of Plan Assets at January 1	285,074	247,713
Actual Return on Plan Assets	42,396	9,443
Employer contributions	19,028	46,766
Benefits Paid	(23,624)	(18,848)
Value of Plan Assets at December 31	322,874	285,074	247,713
Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Accrued benefit cost	(49,326)	(45,129)
Prior service cost (credit)	45,938	62,920
Accumulated gain (loss)	(1,531)	1,795
Total not yet recognized as a component of net periodic benefit cost	44,407	64,715
Current liability	(4,240)	(2,820)
Noncurrent liability	(45,086)	(42,309)
Pension and Other Postretirement Defined Benefit Plans, Liabilities	(49,326)	(45,129)
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit Obligations at January 1	45,129	39,633
Service cost	2,142	3,917	1,509
Interest cost	2,020	3,279	2,083
Plan Amendments	2,183
Benefits Paid	(4,244)	(1,669)
Curtailments	(708)
Acquisition of ICG		48,441
Other-primary actuarial loss (gain)	2,804	7,070
Benefit Obligations at December 31	49,326	45,129	39,633
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Value of Plan Assets at January 1	0	0
Actual Return on Plan Assets	0	0
Employer contributions	4,244	1,669
Benefits Paid	(4,244)	(1,669)
Value of Plan Assets at December 31	0	0	0
Defined Benefit Plan, Effect of Plan Amendment on Accumulated Benefit Obligation		$ (55,542)