Consolidated Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015
Operating Activities
Net Income (Loss)	$ (166,357)	$ (127,021)
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation, depletion and amortization	236,397	284,224
Asset impairment	220,025	66,996
Accretion of discount on asset retirement obligations	3,536	3,679
Deferred income taxes	(93,018)	(67,734)
Change in derivative fair value	64,159	156,135
Gain on sale of assets	(161,110)	(27,503)
Stock-based compensation expense	7,975	11,107
Exploration, including dry holes	16	6,498
Other, net	3,558	7,474
Net change in:
Accounts receivable	35,415	52,036
Inventories	(876)	(3,737)
Accounts payable	(16,619)	(15,413)
Accrued taxes/income tax receivable	19,259	790
Pension contributions	(14,546)	(10,902)
Other current assets and liabilities	(16,989)	(558)
Net cash provided by operating activities	120,825	336,071
Investing Activities
Additions to oil and natural gas properties	(228,204)	(728,284)
Acquisitions, net of cash acquired	(27,765)	(46,203)
Proceeds from the sale of assets, net	285,497	393,094
Purchase of short-term investments	0	(919,000)
Sale of short-term investments	0	919,000
Net cash provided by (used in) investing activities	29,528	(381,393)
Financing Activities
Payment of dividends on common stock	0	(2,923)
Issuance of common stock, net	381,219	399,272
Net change in credit facility	(222,500)	(352,000)
Tax benefit on stock compensation	(455)	631
Net cash provided by financing activities	158,264	44,980
Net change in cash and cash equivalents	308,617	(342)
Cash and cash equivalents at beginning of period	1,272	1,852
Cash and cash equivalents at end of period	$ 309,889	$ 1,510