CONDENSED CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
Current assets:
Cash and cash equivalents	$ 76,506	$ 43,012
Accounts receivable, net of allowance for doubtful accounts of $3,537 and $3,546 at June 30, 2015 and December 31, 2014, respectively	331,922	663,404
Federal and state income taxes receivable		81,726
Inventory	22,672	32,251
Deferred tax assets, net	33,879	37,075
Other	50,815	51,624
Total current assets	515,794	909,092
Property and equipment, net	4,246,147	4,131,071
Goodwill and intangible assets	218,992	220,813
Deposits on equipment purchases	47,741	112,379
Other	20,854	20,656
Total assets	5,049,528	5,394,011
Current liabilities:
Accounts payable	223,001	382,438
Federal and state income taxes payable	11,153
Accrued expenses	171,453	173,466
Current portion of long-term debt	42,500	12,500
Total current liabilities	448,107	568,404
Borrowings under revolving credit facility		303,000
Other long-term debt	830,000	670,000
Deferred tax liabilities, net	892,239	935,660
Other	11,170	11,137
Total liabilities	$ 2,181,516	$ 2,488,201
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 190,406,843 and 189,262,876 issued and 147,199,603 and 146,444,291 outstanding at June 30, 2015 and December 31, 2014, respectively	$ 1,904	$ 1,893
Additional paid-in capital	999,622	984,674
Retained earnings	2,772,613	2,811,815
Accumulated other comprehensive income	918	6,463
Treasury stock, at cost, 43,207,240 shares and 42,818,585 shares at June 30, 2015 and December 31, 2014, respectively	(907,045)	(899,035)
Total stockholders' equity	2,868,012	2,905,810
Total liabilities and stockholders' equity	$ 5,049,528	$ 5,394,011

Carrying value as of the balance sheet date of liabilities incurred (and for which invoices have typically been received) and payable to vendors for goods and services received that are used in an entity's business. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer).

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- Definition

Amount due from customers or clients, within one year of the balance sheet date (or the normal operating cycle, whichever is longer), for goods or services (including trade receivables) that have been delivered or sold in the normal course of business, reduced to the estimated net realizable fair value by an allowance established by the entity of the amount it deems uncertain of collection.