Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017
Cash flows from operating activities:
Net loss	$ (211,638)	$ (76,398)
Adjustments to reconcile net loss to net cash provided by (used in) operating activities:
Depreciation, depletion and amortization	52,431	76,064
Accretion of asset retirement obligation and receivable	17,302	22,437
Share-based compensation	1,860	2,480
Loss on impairment	143,324	0
Non-cash interest expense	4,782	4,639
Amortization of deferred financing costs	5,162	5,193
Non-cash loss on extinguishment of debt	1,420	0
Gain on derivative instruments	0	(1,904)
(Gain) loss on foreign exchange	(1,575)	1,602
Income from equity affiliates	(1,109)	(2,919)
Distributions from equity affiliates	1,262	3,403
Deferred income tax benefit	(712)	(774)
Other	182	(1,752)
Changes in operating assets and liabilities:
Receivables	13,826	11,360
Inventories	(33,275)	7,706
Accounts payable and accrued expenses	(14,403)	(20,919)
Interest payable	6,715	532
Deferred revenue	2,908	(4,924)
Unbilled revenues	12,234	(12,449)
Other assets and liabilities	(20,602)	17,596
Asset retirement obligation	(20,176)	(20,819)
Net cash (used in) provided by operating activities	(40,082)	10,154
Cash flows from investing activities:
Additions to property, plant and equipment	(11,773)	(13,104)
Proceeds from sales of restricted investments	23,623	21,605
Purchases of restricted investments	(23,252)	(24,731)
Cash payments related to acquisitions and other	0	(3,580)
Proceeds from sales of assets	2,087	783
Receipts from loan and lease receivables	0	50,488
Other	(399)	(969)
Net cash (used in) provided by investing activities	(9,714)	30,492
Cash flows from financing activities:
Borrowings from long-term debt, net of debt discount	86,700	0
Repayments of long-term debt	(66,996)	(44,324)
Borrowings on revolving lines of credit	122,400	113,200
Repayments of revolving lines of credit	(122,400)	(113,200)
Debt issuance costs and other refinancing costs	(2,664)	0
Other	0	(364)
Net cash provided by (used in) financing activities	17,040	(44,688)
Effect of exchange rate changes on cash	1,186	463
Net (decrease) increase in cash and cash equivalents, including restricted cash	(31,570)	(3,579)
Cash and cash equivalents, including restricted cash, beginning of period	152,439	129,615
Cash and cash equivalents, including restricted cash, end of period	120,869	126,036
Supplemental disclosures of cash flow information:
Cash paid for interest	41,978	48,931
Non-cash transactions:
Accrued purchases of property and equipment	5,495	1,009
Capital leases and other financing sources	0	480
San Juan longwall financing	8,643	0
Cash and cash equivalents, including restricted cash, end of period
Cash and cash equivalents, including restricted cash, end of period	$ 152,439	$ 129,615