Fair Value of Financial Instruments - Additional Information (Detail) - USD ($)	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Transfer of financial assets	$ 0	$ 0	$ 0	$ 0
Transfer of financial liabilities	$ 0	$ 0	$ 0	$ 0
Fair Value [Member] | Level 1 [Member] | Senior Unsecured Notes Due 2028 [Member]
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Senior unsecured notes, due year			2028		2028