Condensed Consolidated Balance Sheets (USD $) In Thousands, unless otherwise specified	Mar. 31, 2012	Dec. 31, 2011
Current assets:
Cash and cash equivalents	$ 29,159	$ 15,028
Short-term investments	39,948	39,939
Accounts receivable, net	311,357	254,799
Income tax receivable	0	4,903
Inventories	16,736	17,916
Prepaid and other current assets	9,014	9,609
Total current assets	406,214	342,194
Property and equipment, net	350,802	350,725
Goodwill	1,402,056	1,389,965
Other	33,438	34,776
Total assets	2,192,510	2,117,660
Current liabilities:
Current installments of long-term obligations	463,536	397,132
Accounts payable	49,578	53,294
Accrued expenses:
Compensation and benefits	23,461	33,142
Liability insurance	20,227	19,990
Income taxes payable	18,753	0
Other current liabilities	57,815	54,316
Deferred income taxes	4,196	8,769
Total current liabilities	637,566	566,643
Long-term obligations, excluding current installments	263,438	256,778
Deferred income taxes and other taxes	418,686	408,325
Total liabilities	1,319,690	1,231,746
Commitments and contingencies:
Stockholders' equity:
Common stock	864	870
Additional paid-in capital	713,051	707,080
Retained earnings	158,953	177,964
Accumulated other comprehensive income (loss)	(48)	0
Total stockholders' equity	872,820	885,914
Total liabilities and stockholders' equity	$ 2,192,510	$ 2,117,660