Employee Benefit Plans Benefit Obligation And Funded Status (Details) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011
Pension Plans, Defined Benefit [Member]
Change in Benefit Obligation:
Obligation beginning of period	$ 536,536,000	$ 478,790,000
Service cost	11,488,000	10,199,000
Interest cost	23,823,000	24,394,000
Plan amendments	0	0
Actuarial loss (gain)	59,071,000	44,586,000
Benefits paid	(21,275,000)	(21,433,000)
Benefit obligation end of period	609,643,000	536,536,000
Amounts recognized in balance sheet consist of:
Current liability	0	0
Noncurrent liability	(136,707,000)	(103,899,000)
Net amount recognized	(136,707,000)	(103,899,000)
Amounts recognized in AOCI consist of:
Prior service cost	0	0
Net actuarial gain	0	0
Total	(161,604,000)	(131,303,000)
Plans with Benefit Obligations in Excess of Plan Assets [Abstract]
Projected benefit obligation	609,600,000	536,500,000
Accumulated benefit obligation	606,200,000	533,500,000
Fair value of plan assets	472,900,000	432,600,000
Pension Plans, Defined Benefit [Member] | Pension Costs [Member]
Amounts recognized in regulatory assets consist of:
Prior service (cost) credit	(994,000)	(1,241,000)
Net actuarial loss	(160,610,000)	(130,062,000)
Pension Plans, Defined Benefit [Member] | Change During Period, Fair Value Disclosure [Member]
Change in Benefit Obligation:
Benefits paid	(21,275,000)	(21,433,000)
Change in Fair Value of Plan Assets:
Fair value of plan assets at beginning of period	432,637,000	428,152,000
Return on plan assets	49,874,000	14,218,000
Employer contributions	11,700,000	11,700,000
Fair value of plan assets at end of period	472,936,000	432,637,000
Funded Status	(136,707,000)	(103,899,000)
Other Postretirement Benefit Plans, Defined Benefit [Member]
Change in Benefit Obligation:
Obligation beginning of period	32,427,000	35,968,000
Service cost	541,000	437,000
Interest cost	1,167,000	1,348,000
Plan amendments	0	(464,000)
Actuarial loss (gain)	2,508,000	(2,056,000)
Benefits paid	(2,603,000)	(2,806,000)
Benefit obligation end of period	34,040,000	32,427,000
Amounts recognized in balance sheet consist of:
Current liability	(1,082,000)	(1,075,000)
Noncurrent liability	(17,065,000)	(15,850,000)
Net amount recognized	(18,147,000)	(16,925,000)
Amounts recognized in AOCI consist of:
Prior service cost	(1,453,000)	(1,604,000)
Net actuarial gain	(2,432,000)	(1,051,000)
Total	8,023,000	10,865,000
Other Postretirement Benefit Plans, Defined Benefit [Member] | Pension Costs [Member]
Amounts recognized in regulatory assets consist of:
Prior service (cost) credit	21,396,000	23,545,000
Net actuarial loss	(9,488,000)	(10,025,000)
Other Postretirement Benefit Plans, Defined Benefit [Member] | Change During Period, Fair Value Disclosure [Member]
Change in Benefit Obligation:
Benefits paid	(2,603,000)	(2,806,000)
Change in Fair Value of Plan Assets:
Fair value of plan assets at beginning of period	15,502,000	17,201,000
Return on plan assets	1,789,000	340,000
Employer contributions	1,205,000	767,000
Fair value of plan assets at end of period	15,893,000	15,502,000
Funded Status	$ (18,147,000)	$ (16,925,000)