CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($)	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Cash flows from operating activities:
Net income (loss)	$ 130,972,000	$ (231,459,000)
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Impairments and other valuation losses	0	318,786,000
Depreciation, depletion and amortization	95,816,000	110,636,000
Asset retirement obligation	1,620,000	2,298,000
Deferred tax expense (benefit)	78,312,000	(132,063,000)
Stock compensation	6,288,000	5,528,000
(Gain) loss on derivative instruments	(43,861,000)	(428,000)
Settlements on derivative instruments	(6,060,000)	5,068,000
Changes in non-current assets and liabilities	1,019,000	1,863,000
Other, net	1,728,000	1,362,000
Changes in operating assets and liabilities:
Receivables	(44,662,000)	33,147,000
Other current assets	(2,965,000)	11,982,000
Accounts payable and other current liabilities	31,307,000	(41,315,000)
Net cash provided by operating activities	249,514,000	85,405,000
Cash flows from investing activities:
Oil and gas expenditures	(311,841,000)	(176,395,000)
Sales of oil and gas assets	4,901,000	12,971,000
Sales of other assets	45,000	88,000
Other capital expenditures	(8,082,000)	(9,477,000)
Net cash used by investing activities	(314,977,000)	(172,813,000)
Cash flows from financing activities:
Dividends paid	(7,577,000)	(15,104,000)
Employee withholding taxes paid when directly withholding shares on vested stock awards	(938,000)	(345,000)
Proceeds from exercise of stock options and other	10,000	114,000
Net cash used by financing activities	(8,505,000)	(15,335,000)
Net change in cash and cash equivalents	(73,968,000)	(102,743,000)
Cash and cash equivalents at beginning of period	652,876,000	779,382,000
Cash and cash equivalents at end of period	$ 578,908,000	$ 676,639,000