Property, Plant and Equipment (Tables)

12 Months Ended

Dec. 31, 2015

Property, Plant and Equipment [Abstract]

Schedule of Property, Plant and Equipment

Property, plant and equipment includes the following:

	Weighted Average Useful	December 31,
	Lives (Years)	2015		2014
		(in millions)
Transmission	41	$	2,196	$	2,057
Distribution	30	6,556		6,170
Other	16	1,390		1,166
Total		10,142		9,393
Accumulated depreciation		3,209		3,050
Property, plant and equipment, net		$	6,933	$	6,343

Depreciation and Amortization

The following table presents depreciation and amortization expense for 2015, 2014 and 2013:

	Year Ended December 31,
	2015		2014		2013
	(in millions)
Depreciation expense	$	316	$	295	$	280
Amortization of securitized regulatory assets	365		441		383
Other amortization	24		32		22
Total depreciation and amortization	$	705	$	768	$	685

Asset Retirement Obligation

A reconciliation of the changes in the asset retirement obligation (ARO) liability is as follows:

	December 31,
	2015		2014
	(in millions)
Beginning balance	$	36	$	33
Accretion expense	1		1
Revisions in estimates of cash flows	—		2
Ending balance	$	37	$	36