Summary of Changes in Carrying Amount of Notes Receivable From Employees (Parenthetical) (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended						12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Dec. 31, 2013	Sep. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accelerated recognition of amortization expense	$ 1,628	$ 5,347	$ 9,364	$ 27,568	$ 10,419	$ 427	$ 16,339	$ 38,414	$ 29,557
Notes Receivable From Employees
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accelerated recognition of amortization expense								$ 2,300