Simple Agreements for Future Equity (SAFE) - Summary Of Simple Agreements for Future Equity (Detail) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018
Simple Agreements For Future Equity [Line Items]
Losses reported from changes in fair value in the statement of operations	$ (24,215)	$ (12,345)
SAFEs [Member] \| Changes Measurement [Member]
Simple Agreements For Future Equity [Line Items]
Principal amount, inclusive of accrued interest and changes in fair value, if any	$ 0	$ 122,588

Fair value of financial obligations, including, but not limited to, debt instruments, derivative liabilities, federal funds purchased and sold under agreements to repurchase, securities loaned or sold under agreements to repurchase, financial instruments sold not yet purchased, guarantees, line of credit, loans and notes payable, servicing liability, and trading liabilities.

No definition available.

Name:	us-gaap_FinancialLiabilitiesFairValueDisclosure
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant