Pension Plans And Other Postretirement Benefit Plans (Change in Benefit Obligation and Plan Assets) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Defined Benefit Plan Disclosure [Line Items]
Liability, Defined Benefit Plan, Current	$ (9,151)	$ (11,544)
Liability, Defined Benefit Plan, Noncurrent	(222,537)	(203,566)
Defined Benefit Plan, Accumulated Other Comprehensive Income (Loss), after Tax	(7,866)	(8,090)
Pension Plan And SERP [Member]
Defined Benefit Plan Disclosure [Line Items]
Benefit obligation as of beginning of year	716,561	666,472
Service cost	21,614	20,406	$ 18,302
Interest cost	26,096	27,898	27,544
Actuarial (gain)/loss	(48,641)	39,743
Plan Change	0	3,158
Benefits paid	(44,001)	(41,116)
Benefit obligation as of end of year	671,629	716,561	666,472
Fair value of plan assets as of beginning of year	605,652	540,914
Actual return on plan assets	(40,954)	82,476
Employer contributions	22,000	22,000
Benefits Paid	(42,647)	(39,738)
Fair value of plan assets as of end of year	544,051	605,652	540,914
Funded status	(127,578)	(110,909)
Liability, Defined Benefit Plan, Current	(1,477)	(1,663)
Liability, Defined Benefit Plan, Noncurrent	(126,101)	(109,246)
Liability, Defined Benefit Plan	(127,578)	(110,909)
Accumulated pension benefit obligation	586,398	624,345
Unrecognized prior service cost	2,308	2,066
Unrecognized net actuarial loss	138,516	102,624
Accumulated Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Before Regulatory Asset, Net of Tax	140,824	104,690
Defined Benefit Plan, Accumulated Other Comprehensive Income (Loss), after Tax	7,587	7,665
Less regulatory asset	$ (133,237)	$ (97,025)
Discount rate for benefit obligation	4.31%	3.71%
Discount rate for annual expense	3.71%	4.26%
Expected long-term return on plan assets	5.50%	5.87%
Rate of compensation increase	4.67%	4.69%
Expected return on plan assets	$ (33,018)	$ (31,626)	(27,547)
Other Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Benefit obligation as of beginning of year	132,947	136,453
Service cost	3,188	3,220	3,205
Interest cost	4,831	5,490	6,110
Actuarial (gain)/loss	(610)	(6,020)
Plan Change	0	0
Benefits paid	(6,303)	(6,196)
Benefit obligation as of end of year	134,053	132,947	136,453
Fair value of plan assets as of beginning of year	37,953	33,365
Actual return on plan assets	(1,101)	4,588
Employer contributions	0	0
Benefits Paid	0	0
Fair value of plan assets as of end of year	36,852	37,953	33,365
Funded status	(97,201)	(94,994)
Liability, Defined Benefit Plan, Current	(580)	(529)
Liability, Defined Benefit Plan, Noncurrent	(96,621)	(94,465)
Liability, Defined Benefit Plan	(97,201)	(94,994)
Accumulated pension benefit obligation	0	0
Unrecognized prior service cost	(5,230)	(5,058)
Unrecognized net actuarial loss	52,441	44,382
Accumulated Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Before Regulatory Asset, Net of Tax	47,211	39,324
Defined Benefit Plan, Accumulated Other Comprehensive Income (Loss), after Tax	279	425
Less regulatory asset	$ (46,932)	$ (38,899)
Discount rate for benefit obligation	4.32%	3.72%
Discount rate for annual expense	3.72%	4.23%
Expected long-term return on plan assets	5.20%	5.69%
Expected return on plan assets	$ (1,973)	$ (1,899)	$ (1,861)
Other Postretirement Benefits [Member] | Pre-Age 65 [Member]
Defined Benefit Plan Disclosure [Line Items]
Medical cost trend - initial	6.00%	6.50%
Medical cost trend - ultimate	5.00%	5.00%
Ultimate medical cost trend year	2023	2023
Other Postretirement Benefits [Member] | Post-Age 65 [Member]
Defined Benefit Plan Disclosure [Line Items]
Medical cost trend - initial	6.25%	6.50%
Medical cost trend - ultimate	5.00%	5.00%
Ultimate medical cost trend year	2024	2024
Retirees [Member] | Other Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Benefit obligation as of beginning of year	$ 60,354
Benefit obligation as of end of year	63,796	$ 60,354
Fully eligible employees [Member] | Other Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Benefit obligation as of beginning of year	32,891
Benefit obligation as of end of year	29,902	32,891
Other participants [Member] | Other Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Benefit obligation as of beginning of year	39,702
Benefit obligation as of end of year	$ 40,355	$ 39,702