Property, Plant and Equipment (Tables)

12 Months Ended

Dec. 31, 2018

Property, Plant and Equipment [Abstract]

Property, Pland and Equipment with Useful Life Classification

The following table summarizes the components of the electric generation and distribution assets and other property, plant and equipment (in millions) with their estimated useful lives (in years). The amounts are stated net of all prior asset impairment losses recognized.

		December 31,
	Estimated Useful Life	2018			2017
Electric generation and distribution facilities	7-40	$	22,875		$	21,529
Other buildings	5-72	1,651			1,971
Furniture, fixtures and equipment	3-25	310			284
Other	5-44	406			335
Total electric generation and distribution assets and other		25,242			24,119
Accumulated depreciation		(8,227		)	(7,942		)
Net electric generation and distribution assets and other		$	17,015		$	16,177

Interest Capitalized During Development And Construction

The following table summarizes depreciation expense (including the amortization of assets recorded under capital leases and the amortization of asset retirement obligations) and interest capitalized during development and construction on qualifying assets for the periods indicated (in millions):

Years Ended December 31,	2018		2017		2016
Depreciation expense	$	960	$	1,005	$	1,002
Interest capitalized during development and construction	199		139		118

Net Asset Value Of Regulated And Non-Regulated Assets And Accumulated Depreciation

The following table summarizes regulated and non-regulated generation and distribution property, plant and equipment and accumulated depreciation as of the dates indicated (in millions):

December 31,	2018			2017
Regulated generation, distribution assets and other, gross	$	8,959		$	8,093
Regulated accumulated depreciation	(3,504		)	(3,357		)
Regulated generation, distribution assets and other, net	5,455			4,736
Non-regulated generation, distribution assets and other, gross	16,283			16,026
Non-regulated accumulated depreciation	(4,723		)	(4,585		)
Non-regulated generation, distribution assets and other, net	11,560			11,441
Net electric generation, distribution assets and other	$	17,015		$	16,177

Schedule of Change in Asset Retirement Obligation

The following table presents amounts recognized related to asset retirement obligations for the periods indicated (in millions):

	2018			2017
Balance at January 1	$	368		$	357
Additional liabilities incurred	19			1
Liabilities settled	(14		)	(21		)
Accretion expense	18			16
Change in estimated cash flows	24			25
Other	—			(10		)
Balance at December 31	$	415		$	368