Schedule Of Operating Expenses By Category (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Accounting Policies [Line Items]
Salary and related	$ 72,640	$ 67,826	$ 147,357	$ 134,256
Facilities	15,612	12,796	32,022	28,561
Vehicles	14,533	13,756	29,553	26,420
General supplies/miscellaneous	9,092	7,811	17,927	14,859
Total	$ 111,877	$ 102,189	$ 226,859	$ 204,096