Lease Agreements (Details)	9 Months Ended
	Sep. 30, 2021 USD ($) item	Dec. 31, 2020 USD ($)	Jul. 31, 2017 ft²	Dec. 31, 2014 ft²
Sublease Agreement
Number of lease renewal periods | item	2
Lease renewal term (in years)	5 years
Area of real estate property (square feet) | ft²			9,328	57,000
Expected income from sublease	$ 6,200,000
Right-of-use assets	11,824,000	$ 17,895,000
Lease liability	$ 12,900,000	$ 19,300,000
Weighted average remaining lease term	1 year 3 months 29 days
Leasehold improvement
Sublease Agreement
Right-of-use assets	$ 563,000
Lease liability	$ 563,000