Office Closing and Exit Costs - Summary of Termination Costs (Detail) - USD ($) $ in Thousands	3 Months Ended									12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Statement Of Financial Position [Abstract]
Severance costs										$ (822)	$ 11,706	$ 5,372
Building lease										303	3,147	0
Stock-based compensation										0	217	2,999
Total termination costs	$ (822)	$ 136	$ 5	$ 162	$ 8,780	$ (77)	$ 417	$ 5,950	$ 8,400	$ (519)	$ 15,070	$ 8,371