Property, Plant And Equipment

3 Months Ended

Mar. 31, 2016

Property, Plant And Equipment [Abstract]

Property, Plant And Equipment

(5)   Property, Plant and Equipment:

Property, plant and equipment, net is as follows:

($ in millions)	March 31, 2016		December 31, 2015
Property, plant and equipment	$	18,035	$	17,801
Less:  Accumulated depreciation		(9,540)		(9,308)
Property, plant and equipment, net	$	8,495	$	8,493

Depreciation expense is principally based on the composite group method. Depreciation expense was $240 million and $249 millionfor the three months ended March 31, 2016 and 2015, respectively. We adopted new estimated remaining useful lives for certain plant assets as of October 1, 2015, as a result of an annual independent study of the estimated remaining useful lives of our plant assets, with an insignificant impact to depreciation expense.