Quantitative Information about Significant Unobservable Input used in Fair Value Measurement for Contingent Consideration Liability Measured on Recurring Basis (Detail) (Significant Unobservable Inputs (Level 3) [Member])	3 Months Ended
	Mar. 31, 2013
Minimum [Member]
Business Acquisition, Contingent Consideration [Line Items]
Revenue and expense growth percentage	6.00%
Maximum [Member]
Business Acquisition, Contingent Consideration [Line Items]
Revenue and expense growth percentage	31.00%