Asset Retirement Obligations (Tables)

12 Months Ended

Dec. 31, 2018

Asset Retirement Obligation Disclosure [Abstract]

Schedule of Asset Retirement Obligations [Table Text Block]

AROs consist of the following (in millions):

	As of December 31,
	2018		2017
Trojan decommissioning activities	$	68	$	45
Utility plant	112		109
Non-utility property	17		13
Asset retirement obligations	$	197	$	167

Schedule of Change in Asset Retirement Obligation [Table Text Block]

The following is a summary of the changes in the Company’s AROs (in millions):

	Years Ended December 31,
	2018			2017			2016
Balance as of beginning of year	$	167		$	161		$	151
Liabilities incurred	—			2			1
Liabilities settled	(5		)	(3		)	(3		)
Accretion expense	8			7			7
Revisions in estimated cash flows	27			—			5
Balance as of end of year	$	197		$	167		$	161