Pension Plans And Other Postretirement Benefit Plans (Change in Benefit Obligation and Plan Assets) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Accumulated Other Comprehensive Income (Loss), after Tax	$ (6,650)	$ (7,888)
Pension Plan And SERP [Member]
Defined Benefit Plan Disclosure [Line Items]
Benefit obligation as of beginning of year	634,674	527,004
Service cost	19,791	15,757	$ 19,045
Interest cost	26,117	26,224	23,896
Actuarial (gain)/loss	(35,790)	97,128
Defined Benefit Plan, Plan Amendments	(228)	0
Transfer of accrued vacation	0	0
Cumulative adjustment to reclassify liability	0	0
Benefits paid	(31,061)	(31,439)
Benefit obligation as of end of year	613,503	634,674	527,004
Fair value of plan assets as of beginning of year	539,311	481,502
Actual return on plan assets	(4,305)	55,974
Employer contributions	12,000	32,000
Fair value of plan assets as of end of year	517,234	539,311	481,502
Funded status	(96,269)	(95,363)
Unrecognized net actuarial loss	162,961	175,596
Unrecognized prior service cost	25	256
Prepaid (accrued) benefit cost	66,717	80,489
Additional liability	(162,986)	(175,852)
Accrued benefit liability	(96,269)	(95,363)
Accumulated pension benefit obligation	542,209	551,615
Unrecognized prior service cost	16	166
Unrecognized net actuarial loss	105,925	114,138
Accumulated Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Before Regulatory Asset, Net of Tax	105,941	114,304
Defined Benefit Plan, Accumulated Other Comprehensive Income (Loss), after Tax	6,527	7,820
Less regulatory asset	$ (99,414)	$ (106,484)
Discount rate for benefit obligation	4.57%	4.21%
Discount rate for annual expense	4.21%	5.10%
Expected long-term return on plan assets	5.30%	6.60%
Rate of compensation increase	4.87%	4.87%
Expected return on plan assets	$ (28,299)	$ (32,131)	(27,671)
Defined Benefit Plans Benefits Paid	(29,772)	(30,165)
Other Post-Retirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Benefit obligation as of beginning of year	127,989	108,249
Service cost	2,925	1,844	4,144
Interest cost	5,158	5,226	5,216
Actuarial (gain)/loss	12,668	18,714
Defined Benefit Plan, Plan Amendments	(1,000)	0
Transfer of accrued vacation	0	437
Cumulative adjustment to reclassify liability	(1,521)	0
Benefits paid	(7,424)	(6,481)
Benefit obligation as of end of year	138,795	127,989	108,249
Fair value of plan assets as of beginning of year	31,312	29,732
Actual return on plan assets	(444)	1,580
Employer contributions	0	0
Fair value of plan assets as of end of year	30,868	31,312	29,732
Funded status	(107,927)	(96,677)
Unrecognized net actuarial loss	92,433	82,421
Unrecognized prior service cost	(10,180)	(10,379)
Prepaid (accrued) benefit cost	(25,674)	(24,635)
Additional liability	(82,253)	(72,042)
Accrued benefit liability	(107,927)	(96,677)
Accumulated pension benefit obligation	0	0
Unrecognized prior service cost	(6,617)	(6,747)
Unrecognized net actuarial loss	60,081	53,574
Accumulated Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Before Regulatory Asset, Net of Tax	53,464	46,827
Defined Benefit Plan, Accumulated Other Comprehensive Income (Loss), after Tax	123	68
Less regulatory asset	$ (53,341)	$ (46,759)
Discount rate for benefit obligation	4.57%	4.16%
Discount rate for annual expense	4.16%	5.02%
Expected long-term return on plan assets	6.36%	6.40%
Expected return on plan assets	$ (1,991)	$ (1,903)	$ (1,606)
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	2022	2021
Other Post-Retirement Benefits [Member] | Post-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	2023	2022
Retirees [Member] | Other Post-Retirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Benefit obligation as of beginning of year	$ 58,276
Benefit obligation as of end of year	65,652	$ 58,276
Fully eligible employees [Member] | Other Post-Retirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Benefit obligation as of beginning of year	31,843
Benefit obligation as of end of year	34,498	31,843
Other participants [Member] | Other Post-Retirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Benefit obligation as of beginning of year	37,870
Benefit obligation as of end of year	$ 38,645	$ 37,870