CONDENSED CONSOLIDATED BALANCE SHEET (Unaudited) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Current assets
Cash and cash equivalents	$ 537,485	$ 498,542
Accounts receivable, net	192,783	191,045
Income taxes receivable	1,601	10,298
Inventories	12,095	13,304
Other current assets	4,349	2,692
Total current assets	748,313	715,881
Properties and equipment, net (Successful efforts method)	4,328,360	4,250,125
Equity method investments	135,983	129,524
Other assets	31,732	27,039
TOTAL ASSETS	5,244,388	5,122,569
Current liabilities
Accounts payable	183,305	168,411
Accrued liabilities	14,299	21,492
Interest payable	12,262	27,650
Income taxes payable	1,837	0
Derivative instruments	12,692	40,259
Total current liabilities	224,395	257,812
Long-term debt, net	1,520,870	1,520,530
Deferred income taxes	590,575	579,447
Asset retirement obligations	133,526	131,733
Postretirement benefits	37,042	36,259
Other liabilities	30,801	29,121
Total liabilities	2,537,209	2,554,902
Commitments and contingencies
Stockholders' equity
Common stock: Authorized - 960,000,000 shares of $0.10 par value in 2017 and 2016 Issued - 475,414,452 shares and 475,042,692 shares in 2017 and 2016, respectively	47,541	47,504
Additional paid-in capital	1,728,182	1,727,310
Retained earnings	1,237,289	1,098,703
Accumulated other comprehensive income	1,002	985
Less treasury stock, at cost: 9,892,680 shares in 2016 and 2015, respectively	(306,835)	(306,835)
Total stockholders' equity	2,707,179	2,567,667
TOTAL LIABILITIES AND STOCKHOLDERS' EQUITY	$ 5,244,388	$ 5,122,569