Changes in Level 3 Liabilities Measured at Fair Value on Recurring Basis Using Significant Unobservable Inputs (Detail) (Significant Unobservable Inputs (Level 3), USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012
Contingent Consideration
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning balance	$ 9,571
Contingent payments	(3,288)
Interest expense included in earnings	153
Ending balance	6,436
Deferred Compensation
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning balance	2,073
Contingent payments	(712)
Interest expense included in earnings	33
Ending balance	$ 1,394