Office Closing and Exit Costs - Exit Costs Included in Accrued Liabilities in Consolidated Balance Sheet (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Exit costs included in accrued liabilities in consolidated balance sheet
Beginning balance	$ 11,630	$ 5,372
Accrued severance costs	(822)	11,706	$ 5,372
Accrued building rent	303	3,147
Payments	(8,651)	(8,595)
Ending balance	$ 2,460	$ 11,630	$ 5,372