Commitments and Contingencies - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2019 USD ($) CreditFacility	Dec. 31, 2018 USD ($) CreditFacility	Dec. 31, 2017 USD ($)
Commitments and Contingencies Disclosure [Line Items]
Proceeds from lines of credit	$ 0	$ 0	$ 69,355,000
Letter of Credit
Commitments and Contingencies Disclosure [Line Items]
Number of letters of credit issued to secure office space leases (credit facility) | CreditFacility	6	5
Amount outstanding on letters of credit	$ 9,800,000	$ 3,800,000
Proceeds from lines of credit	$ 0	$ 0