Pension Plans And Other Postretirement Benefit Plans (Change in Benefit Obligation and Plan Assets) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Accumulated Other Comprehensive Income (Loss), after Tax	$ (7,568)	$ (6,650)
Pension Plan And SERP [Member]
Defined Benefit Plan Disclosure [Line Items]
Benefit obligation as of beginning of year	613,503	634,674
Service cost	18,302	19,791	$ 15,757
Interest cost	27,544	26,117	26,224
Actuarial (gain)/loss	39,997	(35,790)
Defined Benefit Plan, Plan Amendments	0	(228)
Cumulative adjustment to reclassify liability	0	0
Benefits paid	(32,874)	(31,061)
Benefit obligation as of end of year	666,472	613,503	634,674
Fair value of plan assets as of beginning of year	517,234	539,311
Actual return on plan assets	43,212	(4,305)
Employer contributions	12,000	12,000
Fair value of plan assets as of end of year	540,914	517,234	539,311
Funded status	(125,558)	(96,269)
Unrecognized net actuarial loss	178,783	162,961
Unrecognized prior service cost	23	25
Prepaid (accrued) benefit cost	53,248	66,717
Additional liability	(178,806)	(162,986)
Accrued benefit liability	(125,558)	(96,269)
Accumulated pension benefit obligation	583,498	542,209
Unrecognized prior service cost	15	16
Unrecognized net actuarial loss	116,209	105,925
Accumulated Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Before Regulatory Asset, Net of Tax	116,224	105,941
Defined Benefit Plan, Accumulated Other Comprehensive Income (Loss), after Tax	7,321	6,527
Less regulatory asset	$ (108,903)	$ (99,414)
Discount rate for benefit obligation	4.26%	4.57%
Discount rate for annual expense	4.57%	4.21%
Expected long-term return on plan assets	5.40%	5.30%
Rate of compensation increase	4.78%	4.87%
Expected return on plan assets	$ (27,547)	$ (28,299)	(32,131)
Defined Benefit Plans Benefits Paid	(31,532)	(29,772)
Other Post-Retirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Benefit obligation as of beginning of year	138,795	127,989
Service cost	3,205	2,925	1,844
Interest cost	6,110	5,158	5,226
Actuarial (gain)/loss	(3,648)	12,668
Defined Benefit Plan, Plan Amendments	0	(1,000)
Cumulative adjustment to reclassify liability	(1,042)	(1,521)
Benefits paid	(6,967)	(7,424)
Benefit obligation as of end of year	136,453	138,795	127,989
Fair value of plan assets as of beginning of year	30,868	31,312
Actual return on plan assets	2,497	(444)
Employer contributions	0	0
Fair value of plan assets as of end of year	33,365	30,868	31,312
Funded status	(103,088)	(107,927)
Unrecognized net actuarial loss	81,979	92,433
Unrecognized prior service cost	(8,981)	(10,180)
Prepaid (accrued) benefit cost	(30,090)	(25,674)
Additional liability	(72,998)	(82,253)
Accrued benefit liability	(103,088)	(107,927)
Accumulated pension benefit obligation	0	0
Unrecognized prior service cost	(5,854)	(6,617)
Unrecognized net actuarial loss	53,303	60,081
Accumulated Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Before Regulatory Asset, Net of Tax	47,449	53,464
Defined Benefit Plan, Accumulated Other Comprehensive Income (Loss), after Tax	247	123
Less regulatory asset	$ (47,202)	$ (53,341)
Discount rate for benefit obligation	4.23%	4.57%
Discount rate for annual expense	4.57%	4.16%
Expected long-term return on plan assets	6.03%	6.36%
Expected return on plan assets	$ (1,861)	$ (1,991)	$ (1,903)
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	2023	2022
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	2024	2023
Retirees [Member] | Other Post-Retirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Benefit obligation as of beginning of year	$ 65,652
Benefit obligation as of end of year	60,670	$ 65,652
Fully eligible employees [Member] | Other Post-Retirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Benefit obligation as of beginning of year	34,498
Benefit obligation as of end of year	34,429	34,498
Other participants [Member] | Other Post-Retirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Benefit obligation as of beginning of year	38,645
Benefit obligation as of end of year	$ 41,354	$ 38,645