Condensed Consolidated Balance Sheets (USD $) In Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2011	Dec. 31, 2010
Current assets:
Cash and cash equivalents	$ 82,146	$ 164,203
Short-term investments	40,000	40,000
Restricted cash	0	345
Accounts receivable, net	233,409	186,001
Income tax receivable	2,460	9,443
Inventories	15,388	13,276
Prepaid and other current assets	7,499	3,542
Deferred income taxes	24,842	26,488
Total current assets	405,744	443,298
Property and equipment, net	337,036	338,778
Goodwill	1,352,243	1,258,065
Other	16,145	7,690
Total assets	2,111,168	2,047,831
Current liabilities:
Current installments of long-term obligations	21,230	619
Accounts payable	56,728	64,078
Accrued expenses:
Compensation and benefits	31,815	39,500
Liability insurance	16,316	19,052
Other current liabilities	54,361	51,501
Total current liabilities	180,450	174,750
Long-term obligations, excluding current installments	511,564	494,271
Deferred income taxes and other taxes	404,305	381,061
Total liabilities	1,096,319	1,050,082
Commitments and contingencies:
Stockholders' equity:
Common stock	948	963
Additional paid-in capital	696,342	681,988
Retained earnings	317,559	314,798
Total stockholders' equity	1,014,849	997,749
Total liabilities and stockholders' equity	$ 2,111,168	$ 2,047,831