Company's Purchased Intangible Assets (Detail) (USD $) In Thousands, unless otherwise specified	1 Months Ended	9 Months Ended	12 Months Ended
	Aug. 31, 2012	Sep. 30, 2012	Dec. 31, 2011
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Intangibles		$ 118,852	$ 60,437
Accumulated Amortization		(22,805)	(15,965)
Net Intangibles		96,047	44,472
Weighted Average Amortization Period (years)	8 years	8 years	8 years
Customer relationships [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Intangibles		104,722	58,027
Accumulated Amortization		(20,359)	(14,056)
Net Intangibles		84,363	43,971
Weighted Average Amortization Period (years)	8 years	8 years	8 years
Trade names [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Intangibles		11,600	1,000
Accumulated Amortization		(1,036)	(639)
Net Intangibles		10,564	361
Weighted Average Amortization Period (years)	8 years	8 years	3 years
Non-compete agreements [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Intangibles		1,230	560
Accumulated Amortization		(597)	(560)
Net Intangibles		633	0
Weighted Average Amortization Period (years)	2 years	2 years	1 year
Proprietary software [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Intangibles		850	850
Accumulated Amortization		(788)	(710)
Net Intangibles		62	140
Weighted Average Amortization Period (years)		2 years	2 years
Favorable Lease Agreements [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Intangibles		450
Accumulated Amortization		(25)
Net Intangibles		$ 425
Weighted Average Amortization Period (years)	2 years	2 years