Leases - Additional Information (Detail) - USD ($) $ in Thousands	1 Months Ended		6 Months Ended
	Feb. 28, 2019	Oct. 31, 2018	Jun. 30, 2019
Lessor Lease Description [Line Items]
Operating Lease, weighted average remaining lease term			3 years 4 months 24 days
Operating lease, weighted average incremental borrowing rate			5.40%
Lease incentive obligation, current			$ 9,042
San Francisco, California [Member]
Lessor Lease Description [Line Items]
Lease expiration date		Sep. 30, 2031	Feb. 28, 2027
Operating lease, options to extend description			The tenant also has two options to extend the lease term for a period of five years each.
Operating lease, options to extend			true
Operating lease, option to extend lease period			5 years
Rental payments to be received	$ 5,100	$ 144,900	$ 167,300
Building occupancy rate by tenant			43.00%
Lease incentive obligation to pay for tenant improvements	$ 800
Percentage of office space leased		17.00%
Lease commencement date		May 31, 2019
San Francisco, California [Member] | Tenant One [Member]
Lessor Lease Description [Line Items]
Lease incentive obligation, current			$ 43,700
San Francisco, California [Member] | Tenant Two [Member]
Lessor Lease Description [Line Items]
Lease incentive obligation, current			$ 2,400
Q4 2017 Restructuring Plan [Member]
Lessor Lease Description [Line Items]
Lease term expiration			2022-11
Lessee option to early terminate lease term			2019-11
Terms of assignment			All terms under the original lease were assigned in full to the assignee, with the assignee becoming primarily liable to make rental payments directly to the landlord. Further, the assignee was required to provide the landlord a security deposit equal to twelve months rent to be used by the landlord in the event of the assignee’s non-performance.
Estimated maximum exposure of the guarantee			$ 1,900