Property, Plant and Equipment (Tables)

12 Months Ended

Dec. 31, 2016

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	2016			2015
Electric generation and distribution facilities	4 - 68	$	25,773		$	24,740
Other buildings	3 - 63	2,034			1,856
Furniture, fixtures and equipment	3 - 31	309			288
Other	2 - 50	423			398
Total electric generation and distribution assets and other		28,539			27,282
Accumulated depreciation		(9,528		)	(8,939		)
Net electric generation and distribution assets and other		$	19,011		$	18,343

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,	2016		2015		2014
Depreciation expense	$	1,105	$	1,064	$	1,154
Interest capitalized during development and construction	125		89		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,	2016			2015
Regulated generation, distribution assets and other, gross	$	11,021		$	10,789
Regulated accumulated depreciation	(4,194		)	(3,984		)
Regulated generation, distribution assets and other, net	6,827			6,805
Non-regulated generation, distribution assets and other, gross	17,518			16,493
Non-regulated accumulated depreciation	(5,334		)	(4,955		)
Non-regulated generation, distribution assets and other, net	12,184			11,538
Net electric generation, distribution assets and other	$	19,011		$	18,343

Schedule of Change in Asset Retirement Obligation

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

	2016			2015
Balance at January 1	$	247		$	209
Additional liabilities incurred	12			43
Liabilities settled	(4		)	(6		)
Accretion expense	15			13
Change in estimated cash flows	86			(7		)
Other	1			(5		)
Balance at December 31	$	357		$	247

Schedule of Jointly Owned Utility Plants

DP&L's undivided ownership interest in the facilities as of December 31, 2016 is as follows ($ in millions):

	DP&L Share	DP&L Investment
Production units:	Ownership	Gross Plant In Service		Accumulated Depreciation		Construction Work In Process
Conesville Unit 4	17%	$	—	$	—	$	—
Killen Station	67%	34		—		2
Miami Fort Units 7 and 8	36%	27		—		7
Stuart Station	35%	24		—		23
Zimmer Station	28%	7		—		9
Transmission	Various	99		66		—
Total		$	191	$	66	$	41