Commitments and Contingencies (Tables)

3 Months Ended

Mar. 31, 2021

Commitments And Contingencies Disclosure [Abstract]

Schedule of Additional Information Related to Operating Leases

The following table contains additional information related to our operating leases:

Location	Approximate Square Footage	Commencement Dates	Expiration Dates
Seattle, WA	48,086	March 2019 to September 2020	December 2026 to April 2028
Cambridge, MA	56,859	March 2019 to May 2020	November 2025 to February 2028
South San Francisco, CA	66,075	December 2019 to October 2020	April 2024 to April 2030

Summary of Lease Costs

The following table summarizes the Company’s lease costs:

	Three Months Ended March 31,
	2021		2020
	(in thousands)
Operating lease cost	$	2,898	$	2,444
Shot-term lease cost		512		470
Variable lease cost		1,087		621
Total lease cost	$	4,497	$	3,535

Reconciliation of Undiscounted Operating Lease Cash Flows by Fiscal Year to Present Value of Operating Lease Liabilities

The following table reconciles the Company’s undiscounted operating lease cash flows by fiscal year, to the present value of the operating lease liabilities as of March 31, 2021 (in thousands):

2021 (remaining 9 months)	$	10,300
2022		15,535
2023		15,989
2024		15,663
2025		15,621
2026 and thereafter		42,616
Total undiscounted lease payments		115,724
Less: imputed interest		(36,950	)
Less: tenant improvement allowances		(8,515	)
Present value of operating lease liabilities	$	70,259