Commitments and Contingencies - Additional Information (Detail)			3 Months Ended
	Nov. 19, 2018 USD ($) ft²	Dec. 11, 2017 ft²	Mar. 31, 2020 USD ($)	Mar. 31, 2019 USD ($)	Mar. 01, 2018 USD ($)
Other Commitments [Line Items]
Indemnification obligations			$ 0
Expenses related to indemnification issues			$ 0
Vancouver Office Operating Lease [Member]
Other Commitments [Line Items]
Expiration of operating lease agreement			2019-01
Consolidated lease rent and facilities expense			$ 100,000	$ 100,000
Vancouver Office Operating Lease [Member] | Vancouver, British Columbia [Member]
Other Commitments [Line Items]
Lease agreement commencement date	Feb. 01, 2019
Area of office space leased | ft²	2,367
Initial term of lease expiration date	Jan. 31, 2023
Operating lease, term of contract	4 years
Operating lease, option to extend, description			The initial term of the Vancouver Lease will expire on January 31, 2023, with an option to extend the term for one further four-year period
Lessee, Operating Lease, Existence of Option to Extend [true false]			true
Operating lease, initial monthly base rent expenses	$ 5,200,000
Operating lease, revised monthly base rent expenses	5,400,000
Construction allowance	14,200,000
Security deposit	$ 18,600,000
Seattle Office Operating Lease [Member]
Other Commitments [Line Items]
Consolidated lease rent and facilities expense			$ 100,000	$ 100,000
Seattle Office Operating Lease [Member] | Pike [Member]
Other Commitments [Line Items]
Area of office space leased | ft²		3,187
Lease agreement			On December 11, 2017, we entered into a lease, or the Seattle Lease, with 520 Pike Street, Inc., or Pike, pursuant to which we leased approximately 3,187 square feet located at Suite 2250 at 520 Pike Tower, Seattle, Washington, 98101, which commenced on March 1, 2018. The initial term of the Seattle Lease will expire at the end of the month on the third anniversary of the Seattle Lease.
Monthly base rent					$ 11,685,000
Monthly base rent, maximum annual increase					12,397,000
Lease, security deposit, annual payment					37,192,000
Lease, security deposit payment, annual decrease					$ 12,397,000
Percentage of profit attributable to lessor			50.00%
Percentage of property if subleased could result in lease termination			50.00%