CONDENSED CONSOLIDATED BALANCE SHEETS (Unaudited) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Current assets:
Cash and cash equivalents	$ 186,557	$ 113,346
Accounts receivable, net of allowance for doubtful accounts of $3,191 and $3,545 at March 31, 2016 and December 31, 2015, respectively	182,781	219,672
Federal and state income taxes receivable	37,321	33,454
Inventory	13,220	14,716
Deferred tax assets, net	35,268	65,121
Other	39,064	40,227
Total current assets	494,211	486,536
Property and equipment, net	3,786,835	3,920,708
Goodwill and intangible assets	91,698	92,609
Deposits on equipment purchases	18,395	22,367
Other	7,031	7,264
Total assets	4,398,170	4,529,484
Current liabilities:
Accounts payable	81,975	82,771
Accrued expenses	154,439	161,611
Current portion of long-term debt, net of debt issuance cost of $530 and $483 at March 31, 2016 and December 31, 2015, respectively	76,970	63,267
Total current liabilities	313,384	307,649
Long-term debt, net of debt issuance cost of $2,941 and $3,350 at March 31, 2016 and December 31, 2015, respectively	764,559	787,900
Deferred tax liabilities, net	822,364	863,833
Other	8,381	8,971
Total liabilities	$ 1,908,688	$ 1,968,353
Commitments and contingencies (see Note 9)
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 190,374,862 and 190,374,801 issued and 147,167,622 and 147,167,561 outstanding at March 31, 2016 and December 31, 2015, respectively	$ 1,904	$ 1,904
Additional paid-in capital	1,018,699	1,011,811
Retained earnings	2,373,339	2,458,554
Accumulated other comprehensive income	2,585	(4,093)
Treasury stock, at cost, 43,207,240 shares at March 31, 2016 and December 31, 2015	(907,045)	(907,045)
Total stockholders' equity	2,489,482	2,561,131
Total liabilities and stockholders' equity	$ 4,398,170	$ 4,529,484