CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Current Assets
Cash and cash equivalents	$ 1,272	$ 1,852
Accounts receivable, net	63,097	157,678
Inventories	11,255	14,251
Assets held for sale	93,739	395,797
Derivative instruments	56,963	322,337
Prepayments and other	20,014	27,445
Total current assets	246,340	919,360
Oil and natural gas properties, successful efforts method
Proved properties	7,611,118	6,903,514
Unproved properties	145,724	142,340
Less accumulated depreciation, depletion and amortization	3,454,510	1,893,106
Oil and natural gas properties, net	4,302,332	5,152,748
Other property and equipment, net	48,358	46,389
Total property, plant and equipment, net	4,350,690	5,199,137
Other postretirement assets	3,881	0
Other assets	12,782	19,761
TOTAL ASSETS	4,613,693	6,138,258
Current Liabilities
Accounts payable	64,742	101,453
Accrued taxes	5,801	5,530
Accrued wages and benefits	28,563	21,553
Accrued capital costs	79,206	207,461
Revenue and royalty payable	60,493	72,047
Liabilities related to assets held for sale	12,789	24,230
Pension liabilities	15,685	24,609
Deferred income taxes	0	79,164
Derivative instruments	459	988
Other	19,783	23,288
Total current liabilities	287,521	560,323
Long-term debt	776,087	1,038,563
Asset retirement obligations	89,990	94,060
Pension and other postretirement liabilities	0	15,935
Deferred income taxes	552,369	1,000,486
Other	11,866	14,287
Total liabilities	$ 1,717,833	$ 2,723,654
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; 81,770,161 shares issued at December 31, 2015 and 75,875,711 shares issued at December 31, 2014	818	759
Premium on capital stock	979,030	564,438
Retained earnings	2,046,016	2,997,821
Accumulated other comprehensive income (loss), net of tax
Pension and postretirement plans	263	(22,870)
Deferred compensation plan	1,965	2,862
Treasury stock, at cost; 3,026,350 shares and 2,980,598 shares at December 31, 2015 and 2014, respectively	(132,232)	(128,406)
Total shareholders’ equity	2,895,860	3,414,604
TOTAL LIABILITIES AND SHAREHOLDERS’ EQUITY	$ 4,613,693	$ 6,138,258