CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
Operating activities:
Net loss	$ (278,109)	$ (106,846)
Adjustments to reconcile net loss to net cash provided by operating activities:
Depreciation, depletion and amortization	103,727	269,997
Amortization of acquired intangibles, net	2,961	(7,026)
Accretion of acquisition-related obligations discount	2,227	3,220
Amortization of debt issuance costs and accretion of debt discount	7,389	6,724
Mark-to-market adjustment for acquisition-related obligations	(17,049)	2,950
(Gain) loss on disposal of assets	(755)	1,372
Gain on assets acquired in an exchange transaction	0	(9,083)
Loss on modification and extinguishment of debt	0	26,459
Asset impairment and restructuring	217,882	22,294
Accretion on asset retirement obligations	14,679	13,079
Employee benefit plans, net	10,605	9,564
Deferred income taxes	33,032	(33,623)
Stock-based compensation	3,121	4,774
Equity loss in affiliates	1,790	2,959
Other, net	92	405
Changes in operating assets and liabilities	(22,654)	(90,086)
Net cash provided by operating activities	78,938	117,133
Investing activities:
Capital expenditures	(91,090)	(83,882)
Proceeds on disposal of assets	1,285	1,048
Purchases of investment securities	(18,607)	(9,899)
Maturity of investment securities	10,653	21,316
Capital contributions to equity affiliates	(2,416)	(4,807)
Other, net	47	93
Net cash used in investing activities	(100,128)	(76,131)
Financing activities:
Proceeds from borrowings on debt	57,500	544,946
Principal repayments of debt	(29,559)	(550,000)
Principal repayments of notes payable	(574)	(821)
Principal repayments of financing lease obligations	(1,614)	(2,100)
Debt issuance costs	0	(5,839)
Common stock repurchases and related expenses	(155)	(4,874)
Other, net	0	914
Net cash provided by (used in) financing activities	25,598	(17,774)
Net increase in cash and cash equivalents and restricted cash	4,408	23,228
Cash and cash equivalents and restricted cash at beginning of period	347,680	477,246
Cash and cash equivalents and restricted cash at end of period	352,088	500,474
Reconciliation of Cash and Cash Equivalents and Restricted Cash
Total cash and cash equivalents and restricted cash shown in the Condensed Consolidated Statements of Cash Flows	$ 352,088	$ 500,474