CONDENSED CONSOLIDATED BALANCE SHEETS (Unaudited) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Current assets:
Cash and cash equivalents	$ 466,608	$ 35,152
Accounts receivable, net of allowance for doubtful accounts of $3,186 and $3,191 at March 31, 2017 and December 31, 2016, respectively	210,431	148,091
Federal and state income taxes receivable	1,878	2,126
Inventory	20,754	20,191
Other	30,273	41,322
Total current assets	729,944	246,882
Property and equipment, net	3,328,788	3,408,963
Goodwill and intangible assets	88,055	88,966
Deposits on equipment purchases	19,106	16,050
Deferred tax assets, net	4,771	4,124
Other	7,955	7,306
Total assets	4,178,619	3,772,291
Current liabilities:
Accounts payable	158,226	125,667
Accrued expenses	135,940	139,148
Total current liabilities	294,166	264,815
Long-term debt, net of debt issuance cost of $1,476 and $1,563 at March 31, 2017 and December 31, 2016, respectively	598,524	598,437
Deferred tax liabilities, net	614,361	650,661
Other	9,959	9,654
Total liabilities	1,517,010	1,523,567
Commitments and contingencies (see Note 11)
Stockholders' equity:
Preferred stock, par value $.01; authorized 1,000,000 shares, no shares issued
Common stock, par value $.01; authorized 300,000,000 shares with 209,729,770 and 191,525,872 issued and 166,329,164 and 148,133,255 outstanding at March 31, 2017 and December 31, 2016, respectively	2,097	1,915
Additional paid-in capital	1,521,438	1,042,696
Retained earnings	2,049,476	2,116,341
Accumulated other comprehensive loss	(85)	(1,134)
Treasury stock, at cost, 43,400,606 and 43,392,617 shares at March 31, 2017 and December 31, 2016, respectively	(911,317)	(911,094)
Total stockholders' equity	2,661,609	2,248,724
Total liabilities and stockholders' equity	$ 4,178,619	$ 3,772,291