Debt - Debt (Parenthetical) (Detail) - USD ($)	Dec. 31, 2021	Dec. 31, 2020
Debt Instrument [Line Items]
Unamortized debt issuance cost	$ 710,000	$ 617,000
Unsecured private placement 3.95% note [Member]
Debt Instrument [Line Items]
Unamortized debt issuance cost	230,000	273,000
Unsecured private placement 3.86% note [Member]
Debt Instrument [Line Items]
Unamortized debt issuance cost	181,000	236,000
Unsecured private placement 4.86% note [Member]
Debt Instrument [Line Items]
Unamortized debt issuance cost	69,000	108,000
Unsecured private placement 2.30% note [Member]
Debt Instrument [Line Items]
Unamortized debt issuance cost	100,000	0
Unsecured private placement 2.37% note [Member]
Debt Instrument [Line Items]
Unamortized debt issuance cost	108,000	0
Unsecured private placement 2.73% note [Member]
Debt Instrument [Line Items]
Unamortized debt issuance cost	$ 22,000	$ 0