Consolidated Balance Sheets (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Current assets:
Cash and cash equivalents	$ 249,509	$ 110,723
Accounts receivable, net of allowance for doubtful accounts of $3,674 and $3,513 at December 31, 2013 and 2012, respectively	451,517	465,517
Inventory	21,248	26,889
Deferred tax assets, net	32,952	52,959
Other	53,424	43,903
Total current assets	808,650	699,991
Property and equipment, net	3,635,541	3,615,383
Goodwill and intangible assets	167,470	171,463
Deposits on equipment purchases	52,560	43,776
Other	22,906	26,298
Total assets	4,687,127	4,556,911
Current liabilities:
Accounts payable	173,150	188,823
Federal and state income taxes payable	10,670	6,158
Accrued expenses	160,457	158,632
Current portion of long-term debt	10,000	6,250
Total current liabilities	354,277	359,863
Long-term debt	682,500	692,500
Deferred tax liabilities, net	887,864	857,302
Other	6,489	6,589
Total liabilities	1,931,130	1,916,254
Commitments and contingencies (see Note 8)
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 186,487,246 and 184,059,900 issued and 144,219,189 and 145,913,162 outstanding at December 31, 2013 and 2012, respectively	1,865	1,841
Additional paid-in capital	913,505	863,558
Retained earnings	2,707,439	2,548,542
Accumulated other comprehensive income	14,076	21,767
Treasury stock, at cost, 42,268,057 shares and 38,146,738 shares at December 31, 2013 and 2012, respectively	(880,888)	(795,051)
Total stockholders' equity	2,755,997	2,640,657
Total liabilities and stockholders' equity	$ 4,687,127	$ 4,556,911