Property, Plant, Equipment and Mine Development (Tables)

3 Months Ended

Mar. 31, 2017

Property, Plant, Equipment and Mine Development, Net [Line Items]

Property, Plant and Equipment [Table Text Block]

Property, plant, equipment and mine development, net, as of March 31, 2017 and December 31, 2016 consisted of the following:

	March 31, 2017			December 31, 2016
	(Dollars in millions)
Land and coal interests	$	10,297.7		$	10,330.8
Buildings and improvements	1,479.3			1,507.6
Machinery and equipment	2,143.8			2,130.2
Less: Accumulated depreciation, depletion and amortization	(5,266.9		)	(5,191.9		)
Total, net	$	8,653.9		$	8,776.7

During the three-months ended March 31, 2017, the Company decreased its estimate for the useful lives of certain property, plant, equipment and mine development assets due to changes in mine closure expectations. The assets impacted by the change in estimate had a net book value of $192.7 million at March 31, 2017.