Operating Leases - Narrative (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Lessee, Lease, Description [Line Items]
Operating Lease Fixed And Variable Lease Payments	$ 75,100	$ 57,900
Operating Lease, Lease Income, Lease Payments	62,900	48,500
Variable lease payments	12,200	9,300
Right-of-use assets	4,300		$ 3,500
Lease liabilities	4,977		$ 3,800
Right of use asset obtained in exchange for operating lease liability upon implementation of ASC 842 on January 1, 2019	0	$ 3,262
Operating Lease, Liability, Payments, Leases Not Commenced	$ 1,900
Lessee, Operating Lease, Lease Not yet Commenced, Term of Contract	5 years
Minimum | Office Leases
Lessee, Lease, Description [Line Items]
Remaining lease term	1 month
Renewal term	3 years
Maximum | Office Leases
Lessee, Lease, Description [Line Items]
Remaining lease term	5 years
Renewal term	5 years