Components of Other Intangible Assets (Detail) (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2012	Dec. 31, 2011
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 44,856	$ 32,869
Accumulated Amortization	10,098	7,827
Customer Relationships
Finite-Lived Intangible Assets [Line Items]
Weighted Average Life	18 years 2 months 12 days
Gross Carrying Amount	44,161	32,520
Accumulated Amortization	9,886	7,771
Other Intangible Assets
Finite-Lived Intangible Assets [Line Items]
Weighted Average Life	3 years
Gross Carrying Amount	695	349
Accumulated Amortization	$ 212	$ 56