Equity and Debt Securities - Additional Information (Details) - USD ($)	9 Months Ended	12 Months Ended
	Sep. 30, 2021	Dec. 31, 2020
Schedule Of Available For Sale And Trading Securities [Line Items]
Gross unrealized loss	$ 1,000,000.0	$ 298,000
Outstanding borrowing amount	15,107,000	$ 15,019,000
Credit losses	0
Margin Account Borrowing
Schedule Of Available For Sale And Trading Securities [Line Items]
Cash equivalent and available for sale debt securities	$ 421,200,000