Consolidated Balance Sheets (Unaudited) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Current Assets
Cash and cash equivalents	$ 35,806	$ 1,272
Accounts receivable, net	61,434	63,097
Inventories	12,185	11,255
Assets held for sale	183,234	93,739
Derivative instruments	18,810	56,963
Prepayments and other	21,772	20,014
Total current assets	333,241	246,340
Oil and natural gas properties, successful efforts method
Proved properties	7,491,304	7,611,118
Unproved properties	117,988	145,724
Less accumulated depreciation, depletion and amortization	3,611,302	3,454,510
Oil and natural gas properties, net	3,997,990	4,302,332
Other property and equipment, net	47,186	48,358
Total property, plant and equipment, net	4,045,176	4,350,690
Other postretirement assets	4,366	3,881
Noncurrent derivative instruments	148	0
Other assets	10,087	10,245
TOTAL ASSETS	4,393,018	4,611,156
Current Liabilities
Accounts payable	47,550	64,742
Accrued taxes	13,230	5,801
Accrued wages and benefits	9,127	28,563
Accrued capital costs	58,221	79,206
Revenue and royalty payable	56,949	60,493
Liabilities related to assets held for sale	14,102	12,789
Pension liabilities	0	15,685
Derivative instruments	5,468	459
Other	13,215	19,783
Total current liabilities	217,862	287,521
Long-term debt	551,147	773,550
Asset retirement obligations	90,223	89,990
Deferred income taxes	446,335	552,369
Noncurrent derivative instruments	273	0
Other long-term liabilities	10,718	11,866
Total liabilities	$ 1,316,558	$ 1,715,296
Commitments and Contingencies
Shareholders’ Equity
Preferred stock, cumulative, $0.01 par value, 5,000,000 shares authorized	$ 0	$ 0
Common shareholders’ equity
Common stock, $0.01 par value; 150,000,000 shares authorized; 100,126,767 shares and 81,770,161 shares issued at March 31, 2016 and December 31, 2015, respectively	1,001	818
Premium on capital stock	1,363,178	979,030
Retained earnings	1,842,900	2,046,016
Accumulated other comprehensive income (loss), net of tax
Pension and postretirement plans	2,066	263
Deferred compensation plan	2,246	1,965
Treasury stock, at cost; 3,122,759 shares and 3,026,350 shares at March 31, 2016 and December 31, 2015, respectively	(134,931)	(132,232)
Total shareholders’ equity	3,076,460	2,895,860
TOTAL LIABILITIES AND SHAREHOLDERS’ EQUITY	$ 4,393,018	$ 4,611,156