Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Cash Flows From Operating Activities
Net income	$ 86,737	$ 105,418	$ 76,411
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	313,007	249,845	195,412
Loss on disposal of equipment, net	992	1,586	247
Provision for bad debts and customer credits	4,498	6,300	5,913
Deferred income taxes	(2,102)	(775)	13,991
Deferred rent	11,564	9,259	9,471
Share-based compensation expense	59,645	41,546	28,773
Excess tax benefits from share-based compensation arrangements	(33,539)	(46,046)	(20,627)
Changes in certain assets and liabilities:
Accounts receivable	(34,473)	(29,265)	(26,805)
Prepaid expenses and other current assets	(12,270)	(4,903)	1,800
Accounts payable and accrued expenses	35,303	66,268	38,886
Deferred revenue	5,367	2,185	(482)
All other operating activities	9,331	(1,919)	1,405
Net cash provided by operating activities	444,060	399,499	324,395
Cash Flows From Investing Activities
Purchases of property and equipment	(452,596)	(270,374)	(251,214)
Acquisitions, net of cash acquired	(9,930)	(5,945)	(952)
All other investing activities	(1,698)	98	168
Net cash used in investing activities	(464,224)	(276,221)	(251,998)
Cash Flows From Financing Activities
Principal payments of capital leases	(65,860)	(75,928)	(65,778)
Principal payments of notes payable	(1,915)	(1,962)	(1,913)
Payments for debt issuance costs	0	0	(1,114)
Payments for deferred acquisition obligations	(1,353)	(6,176)	(5,299)
Proceeds from notes payable	0	691	0
Receipt of Texas Enterprise Fund Grant	0	3,500	0
Proceeds from employee stock plans	23,817	41,284	36,287
Excess tax benefits from share-based compensation arrangements	33,539	46,046	20,627
Net cash provided by (used in) financing activities	(11,772)	7,455	(17,190)
Effect of exchange rate changes on cash and cash equivalents	(392)	1,472	(292)
Increase (decrease) in cash and cash equivalents	(32,328)	132,205	54,915
Cash and cash equivalents, beginning of period	292,061	159,856	104,941
Cash and cash equivalents, end of period	259,733	292,061	159,856
Supplemental cash flow information:
Acquisition of property and equipment by vendor financed capital leases	7,190	59,833	75,090
Acquisition of property and equipment by vendor financed notes payable	0	3,950	0
Increase in property and equipment in accounts payable and accrued expenses	12,303	3,525	18,590
Non-cash purchases of property and equipment	19,493	67,308	93,680
Shares issued in business combinations	4,457	2,745	0
Cash payments for interest, net of amount capitalized	3,234	4,900	5,577
Cash payments for income taxes	$ 15,670	$ 12,574	$ 19,088