Property, Plant and Equipment

12 Months Ended

Dec. 31, 2015

Property, Plant and Equipment [Abstract]

Property, Plant and Equipment Disclosure [Text Block]

Property, Plant and Equipment

(a) Property, Plant and Equipment

Property, plant and equipment includes the following:

	Weighted Average Useful Lives	December 31,
	(Years)	2015		2014
		(in millions)
Natural Gas Distribution	32	$	5,762	$	5,235
Energy Services	27	86		84
Other property	10	50		45
Total		5,898		5,364
Accumulated depreciation and amortization:
Natural Gas Distribution		1,575		1,493
Energy Services		34		31
Other property		31		30
Total accumulated depreciation and amortization		1,640		1,554
Property, plant and equipment, net		$	4,258	$	3,810

(b) 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	$	211	$	195	$	218
Amortization expense	16		11		12
Total depreciation and amortization expense	$	227	$	206	$	230

(c) Asset Retirement Obligations

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

	December 31,
	2015		2014
	(in millions)
Beginning balance	$	139	$	101
Accretion expense	5		4
Revisions in estimates of cash flows	12		34
Ending balance	$	156	$	139

CERC recorded AROs associated with the removal of asbestos and asbestos-containing material in its buildings. CERC also recorded AROs relating to gas pipelines abandoned in place.  The estimates of future liabilities were developed using historical information, and where available, quoted prices from outside contractors.

The increase of $12 million in the ARO from the revision of estimate in 2015 is primarily attributable to a reduction in the estimated service lives of steel and plastic pipe. The decrease of $34 million in the ARO from the revision of estimate in 2014 is primarily attributable to a reduction in the estimated service lives of steel and plastic pipe. There were no material additions or settlements during the years ended December 31, 2015 or 2014.