Employee Benefit Plans (Schedule Of Defined Benefit Plans Disclosures) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Defined Benefit Plan Disclosure [Line Items]
Value of plan assets at December 31	$ 285,074	$ 247,713
Accumulated gain (loss)	5,500	(2,000)
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Benefit obligations at January 1	297,707	280,693
Service cost	16,490	15,870	13,444
Interest cost	16,253	15,822	15,946
Plan amendments	(3,235)	(92)
Benefits paid	(18,848)	(15,924)
Acquisition of ICG
Other-primarily actuarial loss (gain)	25,584	1,338
Benefit obligations at December 31	333,951	297,707	280,693
Value of plan assets at January 1	247,713	211,899
Actual return on plan assets	9,443	34,401
Employer contributions	46,766	17,337
Value of plan assets at December 31	285,074	247,713	211,899
Accrued benefit cost	(48,877)	(49,994)
Prior service credit (cost)	1,736	(1,310)
Accumulated gain (loss)	(68,302)	(39,099)
Total not yet recognized as a component of net periodic benefit cost	(66,566)	(40,409)
Current liability	(633)	(840)
Noncurrent liability	(48,244)	(49,154)
Pension and other postretirement defined benefit plans, liabilities	(48,877)	(49,994)
Other Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Benefit obligations at January 1	39,633	46,445
Service cost	3,917	1,509	2,954
Interest cost	3,279	2,083	3,667
Plan amendments	(55,542)
Benefits paid	(1,669)	(1,845)
Acquisition of ICG	48,441
Other-primarily actuarial loss (gain)	7,070	(8,559)
Benefit obligations at December 31	45,129	39,633	46,445
Value of plan assets at January 1
Actual return on plan assets
Employer contributions	1,669	1,845
Value of plan assets at December 31
Accrued benefit cost	(45,129)	(39,633)
Prior service credit (cost)	62,920	9,742
Accumulated gain (loss)	1,795	11,965
Total not yet recognized as a component of net periodic benefit cost	64,715	21,707
Current liability	(2,820)	(1,840)
Noncurrent liability	(42,309)	(37,793)
Pension and other postretirement defined benefit plans, liabilities	$ (45,129)	$ (39,633)