Consolidated Balance Sheets - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
Current Assets
Cash and cash equivalents	$ 1,510	$ 1,852
Accounts receivable, net of allowance for doubtful accounts of $742 and $688 at June 30, 2015 and December 31, 2014, respectively	128,564	157,678
Inventories	17,988	14,251
Assets held for sale	0	395,797
Derivative instruments	147,789	322,337
Prepayments and other	22,419	27,445
Total current assets	318,270	919,360
Oil and natural gas properties, successful efforts method
Proved properties	7,537,545	6,903,514
Unproved properties	168,289	142,340
Less accumulated depreciation, depletion and amortization	2,212,325	1,893,106
Oil and natural gas properties, net	5,493,509	5,152,748
Other property and equipment, net	46,773	46,389
Total property, plant and equipment, net	5,540,282	5,199,137
Other assets	14,094	19,761
TOTAL ASSETS	5,872,646	6,138,258
Current Liabilities
Accounts payable	94,953	101,453
Accrued taxes	14,055	5,530
Accrued wages and benefits	22,217	21,553
Accrued capital costs	110,485	207,461
Revenue and royalty payable	62,179	72,047
Liabilities related to assets held for sale	0	24,230
Pension liabilities	29,616	24,609
Deferred income taxes	11,970	79,164
Derivative instruments	10,220	988
Other	23,220	23,288
Total current liabilities	378,915	560,323
Long-term debt	686,575	1,038,563
Asset retirement obligations	99,049	94,060
Pension and other postretirement liabilities	634	15,935
Deferred income taxes	1,001,251	1,000,486
Noncurrent derivative instruments	3,902	0
Other long-term liabilities	12,272	14,287
Total liabilities	$ 2,182,598	$ 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; 81,767,121 shares and 75,875,711 shares issued at June 30, 2015 and December 31, 2014, respectively	818	759
Premium on capital stock	971,737	564,438
Retained earnings	2,867,877	2,997,821
Accumulated other comprehensive income (loss), net of tax
Pension and postretirement plans	(20,443)	(22,870)
Deferred compensation plan	1,921	2,862
Treasury stock, at cost; 3,019,245 shares and 2,980,598 shares at June 30, 2015 and December 31, 2014, respectively	(131,862)	(128,406)
Total shareholders’ equity	3,690,048	3,414,604
TOTAL LIABILITIES AND SHAREHOLDERS’ EQUITY	$ 5,872,646	$ 6,138,258