Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Operating Activities
Net Loss	$ (203,116)	$ (15,420)
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation, depletion and amortization	119,362	134,381
Asset impairment	220,025	6,583
Accretion of discount on asset retirement obligations	1,757	2,010
Deferred income taxes	(107,149)	(16,009)
Change in derivative fair value	(5,151)	30,987
(Gain) loss on sale of assets	52	(28,502)
Stock-based compensation expense	2,471	5,080
Other, net	2,377	(10,944)
Net change in:
Accounts receivable	50,101	42,908
Inventories	(465)	(3,512)
Accounts payable	(19,611)	(11,814)
Accrued taxes/income tax receivable	2,179	13,633
Pension contributions	(14,516)	(10,872)
Other current assets and liabilities	(27,044)	4,493
Net cash provided by operating activities	21,272	143,002
Investing Activities
Additions to oil and natural gas properties	(137,296)	(395,317)
Acquisitions, net of cash acquired	(7,883)	(30,767)
Proceeds from the sale of assets	187	392,802
Purchase of short-term investments	0	(649,000)
Sale of short-term investments	0	340,000
Net cash used in investing activities	(144,992)	(342,282)
Financing Activities
Payment of dividends on common stock	0	(1,462)
Issuance of common stock, net	381,219	291
Net change in credit facility	(222,500)	200,000
Tax benefit on stock compensation	(465)	129
Net cash provided by financing activities	158,254	198,958
Net change in cash and cash equivalents	34,534	(322)
Cash and cash equivalents at beginning of period	1,272	1,852
Cash and cash equivalents at end of period	$ 35,806	$ 1,530