Operating Revenues (Narrative) (Details)	9 Months Ended
	Sep. 30, 2020
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Customer contracts, average remaining duration	10 years
Minimum
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Customer contracts, term	5 years
Maximum
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Customer contracts, term	15 years