Goodwill and Other Intangible Assets (Tables)

9 Months Ended

Sep. 30, 2018

Goodwill and Intangible Assets Disclosure [Abstract]

Schedule of Changes in Goodwill Assets

The following table summarizes changes in the carrying amount of goodwill for the nine months ended September 30, 2018:

	Regulated Businesses					Market-Based Businesses					Consolidated
	Cost		Accumulated Impairment			Cost		Accumulated Impairment			Cost		Accumulated Impairment			Total Net
Balance as of December 31, 2017	$	3,492	$	(2,332	)	$	327	$	(108	)	$	3,819	$	(2,440	)	$	1,379
Goodwill from acquisitions	—		—			245		—			245		—			245
Goodwill impairment charge	—		—			—		(53		)	—		(53		)	(53		)
Balance as of September 30, 2018	$	3,492	$	(2,332	)	$	572	$	(161	)	$	4,064	$	(2,493	)	$	1,571