Asset Retirement Obligations (Tables)

12 Months Ended

Dec. 31, 2016

Asset Retirement Obligation Disclosure [Abstract]

Schedule of Asset Retirement Obligations [Table Text Block]

AROs consist of the following (in millions):

	As of December 31,
	2016		2015
Trojan decommissioning activities	$	44	$	43
Utility plant	105		97
Non-utility property	12		11
Asset retirement obligations	$	161	$	151

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,
	2016			2015			2014
Balance as of beginning of year	$	151		$	116		$	100
Liabilities incurred	1			2			15
Liabilities settled	(3		)	(4		)	(3		)
Accretion expense	7			7			6
Revisions in estimated cash flows	5			30			(2		)
Balance as of end of year	$	161		$	151		$	116