Description Of Business (Details)	6 Months Ended
	Jun. 30, 2018 mi agreement
Description Of Business [Line Items]
Electrification area | mi	400
International Brotherhood of Electrical Workers [Member]
Description Of Business [Line Items]
Number of collective bargaining agreements	3
Percentage of employees belonging to unions	70.00%
Expiration date of collective bargaining agreements	Jun. 30, 2021
Hotel Employees And Restaurant Employees [Member]
Description Of Business [Line Items]
Number of collective bargaining agreements	1
Expiration date of collective bargaining agreements	Jun. 30, 2021