Condensed Consolidated Statements of Cash Flows - Unaudited - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
Operating activities
Net income (loss)	$ 77,587	$ (213,414)
Adjustments to reconcile net income (loss) to net cash provided by operating activities
Unrealized (gain) loss on derivatives	(33,821)	33,464
Depletion, depreciation and amortization	75,266	60,170
Accretion of asset retirement obligations	614	552
Full-cost ceiling impairment	0	158,633
Stock-based compensation expense	11,192	5,553
Amortization of debt issuance cost	64	592
Net gain on asset sales and inventory impairment	(7)	(2,067)
Changes in operating assets and liabilities
Accounts receivable	(25,642)	(2,751)
Lease and well equipment inventory	(140)	(514)
Prepaid expenses	(2,619)	186
Other assets	165	520
Accounts payable, accrued liabilities and other current liabilities	4,442	2,451
Royalties payable	11,435	153
Advances from joint interest owners	3,768	5,083
Income taxes payable	0	(2,848)
Other long-term liabilities	(1,062)	3,837
Net cash provided by operating activities	121,242	49,600
Investing activities
Oil and natural gas properties capital expenditures	(328,929)	(162,381)
Expenditures for other property and equipment	(41,743)	(47,548)
Proceeds from sale of assets	977	0
Restricted cash	0	43,437
Restricted cash in less-than-wholly-owned subsidiaries	(13,783)	460
Net cash used in investing activities	(383,478)	(166,032)
Financing activities
Proceeds from issuance of common stock	0	142,350
Cost to issue equity	0	(768)
Proceeds from stock options exercised	2,201	0
Contributions related to formation of Joint Venture	171,500	0
Contributions from non-controlling interest owners of less-than-wholly-owned subsidiaries	14,700	0
Distributions to non-controlling interest owners of less-than-wholly-owned subsidiaries	(1,960)	0
Taxes paid related to net share settlement of stock-based compensation	(2,970)	(1,009)
Purchase of non-controlling interest of less-than-wholly-owned subsidiary	(2,653)	0
Net cash provided by financing activities	180,818	140,573
(Decrease) increase in cash	(81,418)	24,141
Cash at beginning of period	212,884	16,732
Cash at end of period	$ 131,466	$ 40,873