Commitments and Contingencies - Additional Information (Detail) - USD ($)	1 Months Ended	12 Months Ended
	Nov. 30, 2015	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Feb. 29, 2012
Commitments And Contingencies [Line Items]
Commitments associated with capital leases		$ 0
Equipment and office rent expense		5,228,000	$ 5,351,000	$ 5,353,000
Uncalled capital commitments to be called over next two year		212,000
Brokerage liability		0	0
Amount of cost related to broker right		0	0	0
Alleged aggregate offering price	$ 151,000,000
Value of pool of assets		3,849,000			$ 3,000,000
Compensation and benefits		77,463,000	103,811,000	144,720,000
Stock Compensation Plan [Member]
Commitments And Contingencies [Line Items]
Compensation and benefits		$ 896,000	$ 1,267,000	$ 879,000
Cliff vesting period		4 years