Debt - Debt (Parenthetical) (Detail) - USD ($)	Mar. 31, 2023	Dec. 31, 2022
Debt Instrument [Line Items]
Unamortized debt issuance cost	$ 722,000	$ 686,000
Unsecured private placement 3.95% note [Member]
Debt Instrument [Line Items]
Unamortized debt issuance cost	175,000	186,000
Unsecured private placement 3.86% note [Member]
Debt Instrument [Line Items]
Unamortized debt issuance cost	112,000	125,000
Unsecured private placement 4.86% note [Member]
Debt Instrument [Line Items]
Unamortized debt issuance cost	19,000	30,000
Unsecured private placement 2.30% note [Member]
Debt Instrument [Line Items]
Unamortized debt issuance cost	116,000	122,000
Unsecured private placement 2.37% note [Member]
Debt Instrument [Line Items]
Unamortized debt issuance cost	122,000	128,000
Unsecured private placement 2.73% note [Member]
Debt Instrument [Line Items]
Unamortized debt issuance cost	102,000	55,000
Unsecured private placement 2.83% note [Member]
Debt Instrument [Line Items]
Unamortized debt issuance cost	$ 76,000	$ 40,000