Debt - Debt (Parenthetical) (Detail) - USD ($)	Mar. 31, 2022	Dec. 31, 2021
Debt Instrument [Line Items]
Unamortized debt issuance cost	$ 812,000	$ 710,000
Unsecured private placement 3.95% note [Member]
Debt Instrument [Line Items]
Unamortized debt issuance cost	218,000	230,000
Unsecured private placement 3.86% note [Member]
Debt Instrument [Line Items]
Unamortized debt issuance cost	167,000	181,000
Unsecured private placement 4.86% note [Member]
Debt Instrument [Line Items]
Unamortized debt issuance cost	60,000	69,000
Unsecured private placement 2.30% note [Member]
Debt Instrument [Line Items]
Unamortized debt issuance cost	138,000	100,000
Unsecured private placement 2.37% note [Member]
Debt Instrument [Line Items]
Unamortized debt issuance cost	145,000	108,000
Unsecured private placement 2.73% note [Member]
Debt Instrument [Line Items]
Unamortized debt issuance cost	62,000	22,000
Unsecured private placement 2.83% note [Member]
Debt Instrument [Line Items]
Unamortized debt issuance cost	$ 22,000	$ 0