Termination Costs - Termination Costs Included in Accrued Liabilities in Consolidated Balance Sheet - (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Exit costs included in accrued liabilities in consolidated balance sheet
Beginning balance	$ 0	$ 1,855
Accrued severance costs	7,535	(356)	$ 2,176
Accrued building rent	0	(17)
Payments	(2,843)	(1,482)
Ending balance	$ 4,692	$ 0	$ 1,855