CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (UNAUDITED) (in thousands) - USD ($) $ in Thousands	3 Months Ended					6 Months Ended			12 Months Ended
	Jun. 30, 2019		Mar. 31, 2019	Jun. 30, 2018	Mar. 31, 2018	Jun. 30, 2019		Jun. 30, 2018	Dec. 31, 2018
Cash flows from operating activities:
Net income (loss)	$ 50,388		$ (177,568)	$ 17,197	$ 317,401	$ (127,180)		$ 334,598
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Net gain on divestiture activity	(262)			(39,501)		(323)		(424,870)
Depletion, depreciation, amortization, and asset retirement obligation liability accretion	206,330			151,765		384,076		282,238
Abandonment and impairment of unproved properties	12,417			11,935		18,755		17,560
Stock-based compensation expense						11,992		10,676
Net derivative loss	(79,655)			63,749		97,426		71,278
Derivative settlement loss						(879)		(61,193)
Amortization of debt discount and deferred financing costs						7,633		7,750
Deferred income taxes	13,766			(861)		(33,237)		97,505
Other, net						(1,287)		(2,302)
Net change working capital						21,454		(21,722)
Net cash provided by operating activities						378,430		311,518
Cash flows from investing activities:
Net proceeds from the sale of oil and gas properties						12,520	[1]	742,215
Capital expenditures						(576,127)		(723,319)
Acquisition of proved and unproved oil and gas properties						319		(24,615)
Net cash used in investing activities						(563,288)		(5,719)
Cash flows from financing activities:
Proceeds from credit facility						696,500		0
Repayment of credit facility						(578,500)		0
Net proceeds from sale of common stock						1,959		1,881
Dividends paid						(5,612)		(5,584)
Other, net						(1,044)		(133)
Net cash provided by (used in) financing activities						113,303		(3,836)
Net change in cash, cash equivalents, and restricted cash						(71,555)		301,963
Cash, cash equivalents, and restricted cash at beginning of period			$ 77,965		$ 313,943	77,965		313,943	$ 313,943
Cash, cash equivalents, and restricted cash at end of period	6,410			615,906		6,410		615,906	77,965
Supplemental Cash Flow Information - Operating activities:
Cash paid for interest, net of capitalized interest						(67,646)		(77,803)
Supplemental Cash Flow Information - Investing activities:
Changes in capital expenditure accruals and other						(10,097)		62,167
Supplemental Cash Flow Information - Non-Cash Investing activities:
Carrying value of properties exchanged						66,588		0
Reconciliation of cash, cash equivalents, and restricted cash:
Cash and cash equivalents	12			615,906		12		615,906	$ 77,965
Restricted cash	$ 6,398	[1]		$ 0		$ 6,398	[1]	$ 0

[1] ⁽¹⁾  As of June 30, 2019, a portion of net proceeds from the sale of oil and gas properties was restricted for future property acquisitions. Restricted cash is included in the other noncurrent assets line item on the accompanying unaudited condensed consolidated balance sheets (“accompanying balance sheets”).