Pension Plans And Other Postretirement Benefit Plans (Change in Benefit Obligation and Plan Assets) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Accumulated Other Comprehensive Income (Loss), after Tax	$ 7,888	$ 4,233
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Benefit obligation as of beginning of year	527,004	584,619
Service cost	15,757	19,045	15,551
Interest cost	26,224	23,896	24,349
Actuarial (gain)/loss	97,128	(78,234)
Defined Benefit Plan, Plan Amendments	0	277
Transfer of accrued vacation	0	0
Benefits paid	(31,439)	(22,599)
Benefit obligation as of end of year	634,674	527,004	584,619
Fair value of plan assets as of beginning of year	481,502	406,061
Actual return on plan assets	55,974	52,502
Employer contributions	32,000	44,263
Fair value of plan assets as of end of year	539,311	481,502	406,061
Funded status	(95,363)	(45,502)
Unrecognized net actuarial loss	175,596	107,043
Unrecognized prior service cost	256	278
Prepaid (accrued) benefit cost	80,489	61,819
Additional liability	(175,852)	(107,321)
Accrued benefit liability	(95,363)	(45,502)
Accumulated pension benefit obligation	551,615	464,432
Unrecognized prior service cost	166	180
Unrecognized net actuarial loss	114,138	69,578
Accumulated Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Before Regulatory Asset, Net of Tax	114,304	69,758
Defined Benefit Plan, Accumulated Other Comprehensive Income (Loss), after Tax	7,820	4,833
Less regulatory asset	(106,484)	(64,925)
Discount rate for benefit obligation	4.21%	5.10%
Discount rate for annual expense	5.10%	4.15%
Expected long-term return on plan assets	6.60%	6.60%
Rate of compensation increase	4.87%	4.96%
Expected return on plan assets	(32,131)	(27,671)	(23,810)
Amortization of transition obligation	0	0	0
Defined Benefit Plans Benefits Paid	(30,165)	(21,324)
Other Post-Retirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Benefit obligation as of beginning of year	108,249	132,541
Service cost	1,844	4,144	2,804
Interest cost	5,226	5,216	5,056
Actuarial (gain)/loss	18,714	(18,017)
Defined Benefit Plan, Plan Amendments	0	(10,788)
Transfer of accrued vacation	437	1,189
Benefits paid	(6,481)	(6,036)
Benefit obligation as of end of year	127,989	108,249	132,541
Fair value of plan assets as of beginning of year	29,732	25,288
Actual return on plan assets	1,580	4,444
Employer contributions	0	0
Fair value of plan assets as of end of year	31,312	29,732	25,288
Funded status	(96,677)	(78,517)
Unrecognized net actuarial loss	82,421	56,885
Unrecognized prior service cost	(10,379)	(707)
Prepaid (accrued) benefit cost	(24,635)	(22,339)
Additional liability	(72,042)	(56,178)
Accrued benefit liability	(96,677)	(78,517)
Accumulated pension benefit obligation	0	0
Unrecognized prior service cost	(6,747)	(7,472)
Unrecognized net actuarial loss	53,574	43,988
Accumulated Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Before Regulatory Asset, Net of Tax	46,827	36,516
Defined Benefit Plan, Accumulated Other Comprehensive Income (Loss), after Tax	68	(600)
Less regulatory asset	(46,759)	(37,116)
Discount rate for benefit obligation	4.16%	5.02%
Discount rate for annual expense	5.02%	4.15%
Expected long-term return on plan assets	6.40%	6.35%
Expected return on plan assets	(1,903)	(1,606)	(1,471)
Amortization of transition obligation	0	0	505
Defined Benefit Plans Benefits Paid	0	0
Other Post-Retirement Benefits [Member] | Pre-Age 65 [Member]
Defined Benefit Plan Disclosure [Line Items]
Medical cost trend - initial	7.00%	7.00%
Medical cost trend - ultimate	5.00%	5.00%
Ultimate medical cost trend year	2021	2020
Other Post-Retirement Benefits [Member] | Post-Age 65 [Member]
Defined Benefit Plan Disclosure [Line Items]
Medical cost trend - initial	7.00%	7.50%
Medical cost trend - ultimate	5.00%	5.00%
Ultimate medical cost trend year	2022	2021
Retirees [Member] | Other Post-Retirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Benefit obligation as of end of year	58,276	52,384
Fully eligible employees [Member] | Other Post-Retirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Benefit obligation as of end of year	31,843	24,320
Other participants [Member] | Other Post-Retirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Benefit obligation as of end of year	$ 37,870	$ 31,545