Office Closing and Termination Costs - Summary of Termination Costs (Detail) - USD ($) $ in Thousands	3 Months Ended			9 Months Ended		12 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2014	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015
Statement Of Financial Position [Abstract]
Termination costs					$ 1,414
Building lease				$ 303	3,156	$ 3,200
Stock-based compensation					1,720
Total termination costs	$ 136	$ (77)	$ 8,400	$ 303	$ 6,290