Commitments and Contingencies (Tables)

12 Months Ended

Dec. 31, 2017

Commitments And Contingencies Disclosure [Abstract]

Schedule of Long-term Commitments

The following is a schedule of future payments under PPAs, minimum lease payments with non-cancelable lease terms in excess of one year, and other net purchase obligations/commitments at December 31, 2017:

					Long-term Service
	Purchased		Operating		Agreements/Capital		Clause Recoverable
(millions)	Power		Leases		Projects		Commitments		Total
Year ended December 31:
2018	$	10	$	2	$	303	$	444	$	759
2019		0		2		74		230		306
2020		0		2		7		177		186
2021		0		2		7		147		156
2022		0		2		7		141		150
Thereafter		0		36		18		1,029		1,083
Total future minimum payments	$	10	$	46	$	416	$	2,168	$	2,640