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Pension Plans And Other Postretirement Benefit Plans (Components Of Net Periodic Benefit Cost) (Details) - USD ($)
$ in Thousands
 3 Months Ended 9 Months Ended
Sep. 30, 2019
Sep. 30, 2018
Sep. 30, 2019
Sep. 30, 2018
Defined Benefit Plan Disclosure [Line Items]        
Percentage of Service Related Net Periodic Benefit Costs Capitalized to Utility Property     40.00%  
Percentage of Service Related Net Periodic Benefit Costs Recorded to Operating Expenses     60.00%  
Percentage of Non-service Related Net Periodic Benefit Costs Capitalized to Regulatory Assets     40.00%  
Percentage of Non-service Related Net Periodic Benefit Costs Recorded to Other Expense     60.00%  
Pension Benefits [Member]        
Defined Benefit Plan Disclosure [Line Items]        
Service cost $ 4,948 $ 5,318 $ 14,770 $ 16,218
Interest cost 7,134 6,634 21,372 19,566
Expected return on plan assets (7,913) (8,101) (23,681) (24,601)
Amortization of prior service cost 75 71 225 221
Net loss recognition 2,553 1,761 7,394 5,691
Net periodic benefit cost 6,797 5,683 20,080 17,095
Other Post-Retirement Benefits [Member]        
Defined Benefit Plan Disclosure [Line Items]        
Service cost 754 815 2,279 2,423
Interest cost 1,140 1,261 3,676 3,655
Expected return on plan assets (616) (550) (1,945) (1,550)
Amortization of prior service cost (275) (299) (825) (905)
Net loss recognition 1,299 1,044 3,874 3,261
Net periodic benefit cost $ 2,302 $ 2,271 $ 7,059 $ 6,884