Debt - Debt (Parenthetical) (Detail) - USD ($)	Jun. 30, 2023	Dec. 31, 2022
Debt Instrument [Line Items]
Unamortized debt issuance cost	$ 660,000	$ 686,000
Unsecured private placement 3.95% note [Member]
Debt Instrument [Line Items]
Unamortized debt issuance cost	164,000	186,000
Unsecured private placement 3.86% note [Member]
Debt Instrument [Line Items]
Unamortized debt issuance cost	98,000	125,000
Unsecured private placement 4.86% note [Member]
Debt Instrument [Line Items]
Unamortized debt issuance cost	0	30,000
Unsecured private placement 2.30% note [Member]
Debt Instrument [Line Items]
Unamortized debt issuance cost	110,000	122,000
Unsecured private placement 2.37% note [Member]
Debt Instrument [Line Items]
Unamortized debt issuance cost	117,000	128,000
Unsecured private placement 2.73% note [Member]
Debt Instrument [Line Items]
Unamortized debt issuance cost	97,000	55,000
Unsecured private placement 2.83% note [Member]
Debt Instrument [Line Items]
Unamortized debt issuance cost	$ 74,000	$ 40,000