Condensed Consolidated Statements of Cash Flows - Unaudited - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017
Statement of Cash Flows [Abstract]
Current period net income	$ 130,561	$ 77,587
Adjustments to reconcile net income to net cash provided by operating activities
Unrealized gain on derivatives	(11,845)	(33,821)
Depletion, depreciation and amortization	122,207	75,266
Accretion of asset retirement obligations	739	614
Stock-based compensation expense	8,945	11,192
Amortization of debt issuance cost	411	64
Net gain on asset sales and inventory impairment	0	(7)
Changes in operating assets and liabilities
Accounts receivable	(9,321)	(25,642)
Lease and well equipment inventory	(8,611)	(140)
Prepaid expenses	(2,167)	(2,619)
Other assets	(149)	165
Accounts payable, accrued liabilities and other current liabilities	(883)	4,442
Royalties payable	8,393	11,435
Advances from joint interest owners	16,025	3,768
Other long-term liabilities	(97)	(1,062)
Net cash provided by operating activities	254,208	121,242
Investing activities
Oil and natural gas properties capital expenditures	(421,595)	(328,929)
Expenditures for midstream and other property and equipment	(79,560)	(41,743)
Proceeds from sale of assets	7,593	977
Net cash used in investing activities	(493,562)	(369,695)
Financing activities
Repayments of borrowings	45,000	0
Borrowings under Credit Agreement	45,000	0
Proceeds from issuance of common stock	226,612	0
Cost to issue equity	73	0
Proceeds from stock options exercised	464	2,201
Contributions related to formation of Joint Venture	14,700	171,500
Contributions from non-controlling interest owners of less-than-wholly-owned subsidiaries	53,900	14,700
Distributions to non-controlling interest owners of less-than-wholly-owned subsidiaries	(10,535)	(1,960)
Taxes paid related to net share settlement of stock-based compensation	(4,683)	(2,970)
Purchase of non-controlling interest of less-than-wholly-owned subsidiary	0	(2,653)
Net cash provided by financing activities	280,385	180,818
Increase (decrease) in cash and restricted cash	41,031	(67,635)
Cash and restricted cash at beginning of period	102,482	214,142
Cash and restricted cash at end of period	$ 143,513	$ 146,507