Property, Plant and Equipment

12 Months Ended

Dec. 31, 2017

Property, Plant and Equipment [Abstract]

At the end of 2017 and 2016, property, plant and equipment at cost and accumulated depreciation were:



(Dollars in Millions)	2017		2016
Land and land improvements	$	829	753
Buildings and building equipment	11,240		10,112
Machinery and equipment	25,949		23,554
Construction in progress	3,448		3,354
Total property, plant and equipment, gross	$	41,466	37,773
Less accumulated depreciation	24,461		21,861
Total property, plant and equipment, net	$	17,005	15,912

The Company capitalizes interest expense as part of the cost of construction of facilities and equipment. Interest expense capitalized in 2017, 2016 and 2015 was $94 million, $102 million and $102 million, respectively.

Depreciation expense, including the amortization of capitalized interest in 2017, 2016 and 2015 was $2.6 billion, $2.5 billion and $2.5 billion, respectively.

Upon retirement or other disposal of property, plant and equipment, the costs and related amounts of accumulated depreciation or amortization are eliminated from the asset and accumulated depreciation accounts, respectively. The difference, if any, between the net asset value and the proceeds are recorded in earnings.