Noncontrolling Interests (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Preferred Securities of Subsidiaries [Line Items]
Preferred stock of subsidiaries, value, outstanding noncontrolling interest, amount represented by preferred stock	$ 58	$ 58
PacifiCorp [Member]
Preferred Securities of Subsidiaries [Line Items]
Preferred stock of subsidiaries, value, outstanding noncontrolling interest, amount represented by preferred stock	2	2
Northern Electric Plc [Member]
Preferred Securities of Subsidiaries [Line Items]
Preferred stock of subsidiaries, value, outstanding noncontrolling interest, amount represented by preferred stock	$ 56	$ 56
Noncontrolling interest, dividend requirements of preferred stock	0.08061	0.08061