Office Closing and Termination Costs - Exit Costs Included in Accrued Liabilities in Consolidated Balance Sheet (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Exit costs included in accrued liabilities in consolidated balance sheet
Beginning balance at December 31, 2016			$ 2,460
Accrued severance costs	$ 0	$ 0	2,422	$ 0
Accrued building rent			(37)
Payments			(2,290)
Ending balance at September 30, 2017	$ 2,555		$ 2,555