Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015
Operating Activities
Net Income (Loss)	$ (113,043)	$ (354,925)
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation, depletion and amortization	344,564	434,005
Asset impairment	220,612	466,390
Accretion of discount on asset retirement obligations	5,092	5,379
Deferred income taxes	(78,159)	(217,943)
Change in derivative fair value	35,366	139,490
Gain on sale of assets	(252,510)	(27,558)
Stock-based compensation expense	14,493	12,040
Exploration, including dry holes	16	6,967
Other, net	3,082	7,080
Net change in:
Accounts receivable	38,947	81,285
Inventories	(2,439)	(3,933)
Accounts payable	(13,592)	(30,871)
Accrued taxes/income tax receivable	37,646	25,339
Pension contributions	(14,576)	(10,932)
Other current assets and liabilities	(23,580)	(9,878)
Net cash provided by operating activities	201,919	521,935
Investing Activities
Additions to oil and natural gas properties	(314,581)	(960,966)
Acquisitions, net of cash acquired	(135,775)	(62,805)
Proceeds from the sale of assets, net	537,202	393,174
Purchase of short-term investments	0	(919,000)
Sale of short-term investments	0	919,000
Net cash provided by (used in) investing activities	86,846	(630,597)
Financing Activities
Payment of dividends on common stock	0	(4,499)
Issuance of common stock, net	381,219	399,593
Net change in credit facility	(222,500)	(288,500)
Tax benefit on stock compensation	(831)	917
Net cash provided by financing activities	157,888	107,511
Net change in cash and cash equivalents	446,653	(1,151)
Cash and cash equivalents at beginning of period	1,272	1,852
Cash and cash equivalents at end of period	$ 447,925	$ 701