Commitments and Contingencies (Tables)

12 Months Ended

Dec. 31, 2016

Commitments and Contingencies Disclosure [Abstract]

Summary of estimated coal take-or-pay commitments

The following table summarizes our estimated coal take-or-pay commitments (dollars in thousands):

	Years Ended December 31,
	2017		2018		2019		2020		2021		Thereafter
Coal take-or-pay commitments (a)	$	195,428	$	189,588	$	193,818	$	198,160	$	202,619	$	2,068,355

(a) Total take-or-pay commitments are approximately $3.0 billion.  The total net present value of these commitments is approximately $2.1 billion.

Summary of actual take-or-pay commitments

	Year Ended December 31,
	2016		2015		2014
Total purchases	$	160,066	$	211,327	$	236,773