PROPERTY AND EQUIPMENT

12 Months Ended

Dec. 31, 2017

Property, Plant and Equipment [Abstract]

PROPERTY AND EQUIPMENT

PROPERTY AND EQUIPMENT

Property and equipment includes land, buildings and improvements, machinery and equipment, roads and other items.

Carrying Value of Property and Equipment and Estimated Service Lives

DOLLAR AMOUNTS IN MILLIONS
	RANGE OF LIVES	DECEMBER 31, 2017			DECEMBER 31, 2016
Property and equipment, at cost:
Land	N/A	$	88		$	90
Buildings and improvements	15-35	867			789
Machinery and equipment	5-25	3,037			3,022
Roads	10-35	782			773
Other	3-10	182			194
Total cost		4,956			4,868
Accumulated depreciation and amortization		(3,338		)	(3,306		)
Property and equipment, net		$	1,618		$	1,562

SERVICE LIVES AND DEPRECIATION

In general, additions are classified into components, each with its own estimated useful life as determined at the time of purchase. Buildings and improvements for property and equipment have estimated lives that are generally at either the high end or low end of the range from 15 years to 35 years, depending on the type and performance of construction.

Depreciation expense, excluding discontinued operations, was:

• $206 million in 2017,

• $198 million in 2016 and

• $160 million in 2015.