Employee Benefit Plans Benefit Obligation And Funded Status (Details) (USD $)	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010
Pension Plans, Defined Benefit [Member]
Change in Benefit Obligation:
Obligation beginning of period	$ 478,790,000	$ 415,278,000
Service cost	10,199,000	9,361,000
Interest cost	24,394,000	24,090,000
Plan amendments	0	0
Actuarial loss (gain)	44,586,000	51,730,000
Benefits paid	(21,433,000)	(21,669,000)
Benefit obligation end of period	536,536,000	478,790,000
Change in Fair Value of Plan Assets:
Benefits paid	(21,433,000)	(21,669,000)
Amounts recognized in balance sheet consist of:
Current liability	0	0
Noncurrent liability	(103,899,000)	(50,638,000)
Net amount recognized	(103,899,000)	(50,638,000)
Amounts recognized in AOCI consist of:
Prior service cost	0	0
Net actuarial gain	0	0
Total	(131,303,000)	(73,236,000)
Plans with Benefit Obligations in Excess of Plan Assets [Abstract]
Projected benefit obligation	536,500,000	478,800,000
Accumulated benefit obligation	533,500,000	475,700,000
Fair value of plan assets	432,600,000	428,200,000
Pension Plans, Defined Benefit [Member] | Pension Costs [Member]
Amounts recognized in regulatory assets consist of:
Prior service (cost) credit	(1,241,000)	(1,487,000)
Net actuarial loss	(130,062,000)	(71,749,000)
Pension Plans, Defined Benefit [Member] | Change During Period, Fair Value Disclosure [Member]
Change in Benefit Obligation:
Benefits paid	(21,433,000)	(21,669,000)
Change in Fair Value of Plan Assets:
Fair value of plan assets at beginning of period	428,152,000	391,429,000
Return on plan assets	14,218,000	48,392,000
Employer contributions	11,700,000	10,000,000
Benefits paid	(21,433,000)	(21,669,000)
Fair value of plan assets at end of period	432,637,000	428,152,000
Funded Status	(103,899,000)	(50,638,000)
Unrecognized net actuarial (gain) loss	0	0
Unrecognized prior service cost	0	0
Accrued benefits cost	(103,899,000)	(50,638,000)
Other Postretirement Benefit Plans, Defined Benefit [Member]
Change in Benefit Obligation:
Obligation beginning of period	35,968,000	32,347,000
Service cost	437,000	483,000
Interest cost	1,348,000	1,803,000
Plan amendments	(464,000)	0
Actuarial loss (gain)	(2,056,000)	4,758,000
Benefits paid	(2,806,000)	(3,423,000)
Benefit obligation end of period	32,427,000	35,968,000
Change in Fair Value of Plan Assets:
Benefits paid	(2,806,000)	(3,423,000)
Amounts recognized in balance sheet consist of:
Current liability	(1,075,000)	(1,078,000)
Noncurrent liability	(15,850,000)	(17,689,000)
Net amount recognized	(16,925,000)	(18,767,000)
Amounts recognized in AOCI consist of:
Prior service cost	(1,604,000)	(1,755,000)
Net actuarial gain	(1,051,000)	(395,000)
Total	10,865,000	10,531,000
Other Postretirement Benefit Plans, Defined Benefit [Member] | Pension Costs [Member]
Amounts recognized in regulatory assets consist of:
Prior service (cost) credit	23,545,000	25,230,000
Net actuarial loss	(10,025,000)	(12,549,000)
Other Postretirement Benefit Plans, Defined Benefit [Member] | Change During Period, Fair Value Disclosure [Member]
Change in Benefit Obligation:
Benefits paid	(2,806,000)	(3,423,000)
Change in Fair Value of Plan Assets:
Fair value of plan assets at beginning of period	17,201,000	15,298,000
Return on plan assets	340,000	1,903,000
Employer contributions	767,000	3,423,000
Benefits paid	(2,806,000)	(3,423,000)
Fair value of plan assets at end of period	15,502,000	17,201,000
Funded Status	(16,925,000)	(18,767,000)
Unrecognized net actuarial (gain) loss	0	0
Unrecognized prior service cost	0	0
Accrued benefits cost	$ (16,925,000)	$ (18,767,000)