Property, Plant and Equipment (Tables)

12 Months Ended

Dec. 31, 2014

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)	2014		2013
		(in millions)
Transmission	41	$	2,057	$	1,926
Distribution	30	6,170		5,848
Other	15	1,166		967
Total		9,393		8,741
Accumulated depreciation		3,050		2,907
Property, plant and equipment, net		$	6,343	$	5,834

Depreciation and Amortization

The following table presents depreciation and amortization expense for 2014, 2013 and 2012:

	Year Ended December 31,
	2014		2013		2012
	(in millions)
Depreciation expense	$	295	$	280	$	265
Amortization of securitized regulatory assets	441		383		442
Other amortization	32		22		22
Total depreciation and amortization	$	768	$	685	$	729

Asset Retirement Obligation

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

	December 31,
	2014		2013
Beginning balance	$	33	$	29
Accretion expense	1		1
Revisions in estimates of cash flows	2		3
Ending balance	$	36	$	33