CONDENSED CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Current assets:
Cash and cash equivalents	$ 641,739	$ 779,382
Receivables, net	229,634	225,398
Oil and gas well equipment and supplies	37,852	54,579
Derivative instruments	1,119	10,745
Prepaid expenses	5,090	7,036
Other current assets	2,173	790
Total current assets	917,607	1,077,930
Oil and gas properties at cost, using the full cost method of accounting:
Proved properties	15,845,260	15,546,948
Unproved properties and properties under development, not being amortized	458,530	440,166
Gross oil and gas properties	16,303,790	15,987,114
Less - accumulated depreciation, depletion, amortization and impairment	(13,569,032)	(12,710,968)
Net oil and gas properties	2,734,758	3,276,146
Fixed assets, net	224,056	230,009
Goodwill	620,232	620,232
Derivative instruments		501
Other assets, net	35,170	38,468
Total assets	4,531,823	5,243,286
Current liabilities:
Accounts payable	55,564	66,815
Accrued liabilities	220,154	247,508
Derivative instruments	28,399
Revenue payable	99,209	95,744
Total current liabilities	403,326	410,067
Principal	1,500,000	1,500,000
Less - unamortized debt issuance costs	(13,205)	(14,380)
Long-term debt, net	1,486,795	1,485,620
Deferred income taxes	92,446	352,705
Other liabilities	202,454	197,216
Total liabilities	2,185,021	2,445,608
Commitments and contingencies
Stockholders' equity:
Preferred stock, $0.01 par value, 15,000,000 shares authorized, no shares issued
Common stock, $0.01 par value, 200,000,000 shares authorized, 94,986,852 and 94,820,570 shares issued, respectively	950	948
Paid-in capital	2,775,805	2,762,976
Retained earnings (Accumulated deficit)	(430,674)	33,313
Accumulated other comprehensive income	721	441
Total stockholders' equity	2,346,802	2,797,678
Total liabilities and stockholders' equity	$ 4,531,823	$ 5,243,286