Property, Plant and Equipment (Tables)

12 Months Ended

Dec. 31, 2016

Property, Plant and Equipment [Abstract]

Schedule of Property, Plant and Equipment [Table Text Block]

Property, plant and equipment includes the following:

	Weighted Average Useful	December 31,
	Lives (in years)	2016		2015
		(in millions)
Transmission	44	$	2,402	$	2,196
Distribution	31	6,965		6,556
Other	14	1,473		1,390
Total		10,840		10,142
Accumulated depreciation		3,443		3,209
Property, plant and equipment, net		$	7,397	$	6,933

Depreciation and Amortization [Table Text Block]

The following table presents depreciation and amortization expense for 2016, 2015 and 2014:

	Year Ended December 31,
	2016		2015		2014
	(in millions)
Depreciation expense	$	349	$	316	$	295
Amortization of securitized regulatory assets	455		365		441
Other amortization	34		24		32
Total depreciation and amortization	$	838	$	705	$	768

Asset Retirement Obligation [Table Text Block]

A reconciliation of the changes in the ARO liability is as follows:

	December 31,
	2016			2015
	(in millions)
Beginning balance	$	37		$	36
Accretion expense	1			1
Revisions in estimates of cash flows	(5		)	—
Ending balance	$	33		$	37