Reconciliation of Segment Revenues and Operating Profit to Consolidated Income from Operations (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Segment Reporting Information [Line Items]
Revenues	$ 110,078	$ 86,423	$ 308,261	$ 239,401
Income from operations	16,736	16,891	47,350	39,581
Stock-based compensation expense	(2,046)	(785)	(5,369)	(2,154)
Depreciation and amortization	(3,040)	(2,083)	(7,674)	(5,732)
Goodwill impairment loss				(1,697)
Operating Segments
Segment Reporting Information [Line Items]
Revenues	110,075	86,412	308,222	239,191
Income from operations	22,158	20,617	63,125	52,048
Unallocated Amount to Segment
Segment Reporting Information [Line Items]
Revenues	3	11	39	210
Other revenues	3	11	39	210
Stock-based compensation expense	(2,046)	(785)	(5,369)	(2,154)
Legal settlement			(640)
Non-corporate taxes	(391)	(584)	(1,630)	(2,179)
Professional fees	(493)	(812)	(1,811)	(2,193)
Depreciation and amortization	(448)	(192)	(756)	(668)
Bank charges	(278)	(200)	(823)	(529)
Goodwill impairment loss				(1,697)
Other corporate expenses	$ (1,769)	$ (1,164)	$ (4,785)	$ (3,257)