Consolidated Balance Sheets (Unaudited) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Current Assets
Cash and cash equivalents	$ 17,057	$ 439
Accounts receivable, net	183,816	158,787
Inventories, net	28,652	13,177
Derivative instruments	4,226	0
Income tax receivable	6,762	6,905
Prepayments and other	5,999	12,085
Total current assets	246,512	191,393
Oil and natural gas properties, successful efforts method
Proved properties	9,387,502	8,466,708
Unproved properties	551,217	453,028
Less accumulated depreciation, depletion and amortization	(4,587,082)	(4,200,797)
Oil and natural gas properties, net	5,351,637	4,718,939
Other property and equipment, net	43,471	44,581
Total property, plant and equipment, net	5,395,108	4,763,520
Other postretirement assets	2,590	2,646
Noncurrent income tax receivable, net	70,716	70,716
Other assets	9,112	5,620
TOTAL ASSETS	5,724,038	5,033,895
Current Liabilities
Accounts payable	129,602	75,167
Accrued taxes	23,509	2,631
Accrued wages and benefits	15,416	26,170
Accrued capital costs	150,600	74,909
Revenue and royalty payable	65,023	54,072
Derivative instruments	172,772	71,379
Other	12,635	17,916
Total current liabilities	569,557	322,244
Long-term debt	953,173	782,861
Asset retirement obligations	94,722	88,378
Noncurrent derivative instruments	57,457	8,886
Deferred income taxes	435,848	387,807
Other long-term liabilities	5,398	5,262
Total liabilities	2,116,155	1,595,438
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; 100,799,082 shares and 100,327,433 shares issued at September 30, 2018 and December 31, 2017, respectively	1,008	1,003
Premium on capital stock	1,405,227	1,388,082
Retained earnings	2,345,491	2,185,161
Accumulated other comprehensive income, net of tax
Postretirement plans	482	380
Deferred compensation plan	3,311	2,681
Treasury stock, at cost; 3,350,023 shares and 3,192,252 shares at September 30, 2018 and December 31, 2017, respectively	(147,636)	(138,850)
Total shareholders’ equity	3,607,883	3,438,457
TOTAL LIABILITIES AND SHAREHOLDERS’ EQUITY	$ 5,724,038	$ 5,033,895