CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (UNAUDITED) (in thousands) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Cash flows from operating activities:
Net income (loss)	$ (177,568)	$ 317,401
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Net gain on divestiture activity	(61)	(385,369)
Depletion, depreciation, amortization, and asset retirement obligation liability accretion	177,746	130,473
Abandonment and impairment of unproved properties	6,338	5,625
Stock-based compensation expense	5,838	5,412
Net derivative loss	177,081	7,529
Derivative settlement loss	(4,969)	(24,528)
Amortization of debt discount and deferred financing costs	3,789	3,866
Deferred income taxes	(47,003)	98,366
Other, net	(2,530)	(2,527)
Net change working capital	(20,159)	(16,113)
Net cash provided by operating activities	118,502	140,135
Cash flows from investing activities:
Net proceeds from the sale of oil and gas properties	6,114	490,780
Capital expenditures	(249,340)	(301,521)
Other, net	291	0
Net cash provided by (used in) investing activities	(242,935)	189,259
Cash flows from financing activities:
Proceeds from credit facility	172,000	0
Repayment of credit facility	(125,500)	0
Other, net	(18)	0
Net cash provided by financing activities	46,482	0
Net change in cash, cash equivalents, and restricted cash	(77,951)	329,394
Cash, cash equivalents, and restricted cash at beginning of period	77,965	313,943	$ 313,943
Cash, cash equivalents, and restricted cash at end of period	14	643,337	$ 77,965
Supplemental Cash Flow Information - Operating activities:
Cash paid for interest, net of capitalized interest	(39,957)	(40,060)
Supplemental Cash Flow Information - Investing activities:
Changes in capital expenditure accruals and other	62,185	60,299
Supplemental Cash Flow Information - Non-Cash Investing activities:
Carrying value of properties exchanged	$ 65,788	$ 0