Notes Payable (Schedule of Long-term Debt) (Details)			3 Months Ended	12 Months Ended
	Apr. 25, 2024 USD ($)	Nov. 18, 2022 USD ($)	Mar. 31, 2024 USD ($)	Dec. 31, 2023 USD ($)	Nov. 30, 2023 USD ($)	Mar. 31, 2021 USD ($)	Mar. 08, 2017 USD ($)
Debt Instrument [Line Items]
Interest rate							4.40%
Total principal amount			$ 575,000,000	$ 575,000,000
Less unamortized discount and debt issuance costs			1,171,000	1,271,000
Notes payable			573,829,000	573,729,000
Debt issuance cost							$ 3,400,000
Debt instrument, discount percent							99.847%
Effective interest rate							4.45%
Unamortized debt issuance cost			800,000
Unsecured Notes Two | Revolving Credit Facility
Debt Instrument [Line Items]
Loan maximum borrowing capacity		$ 200,000,000			$ 250,000,000	$ 75,000,000
Drawn down amount under credit facility			200,000,000	200,000,000
Unsecured Notes Two | Revolving Credit Facility | Consolidated Insurance Subsidiary
Debt Instrument [Line Items]
Drawn down amount under credit facility contributed			150,000,000
Unsecured Notes Two | Revolving Credit Facility | Subsequent Event
Debt Instrument [Line Items]
Effective interest rate	6.79%
Drawn down amount under credit facility	$ 200,000,000
Remaining amount available to be drawn	$ 50,000,000
Unsecured debt
Debt Instrument [Line Items]
Notes payable			$ 373,829,000	373,729,000
Unsecured debt | Notes payable | Level 2 | Unsecured Notes One
Debt Instrument [Line Items]
Interest rate			4.40%
Unsecured debt			$ 375,000,000	375,000,000			$ 375,000,000
Unsecured debt | Notes payable | Level 2 | Unsecured Notes Two
Debt Instrument [Line Items]
Unsecured debt			$ 200,000,000	$ 200,000,000
Minimum | Unsecured Notes Two | Revolving Credit Facility
Debt Instrument [Line Items]
Commitment fee on undrawn portion of facility		0.125%	0.175%
Maximum | Unsecured Notes Two | Revolving Credit Facility
Debt Instrument [Line Items]
Debt to total capital ratio			0.264
Commitment fee on undrawn portion of facility		0.225%
Secured Overnight Financing Rate (SOFR) Overnight Index Swap Rate | Minimum | Unsecured Notes Two | Revolving Credit Facility
Debt Instrument [Line Items]
Basis spread on variable rate			1.125%
Debt to total capital ratio		0.20
Secured Overnight Financing Rate (SOFR) Overnight Index Swap Rate | Minimum | Unsecured debt | Notes payable | Level 2 | Unsecured Notes Two
Debt Instrument [Line Items]
Basis spread on variable rate			1.125%
Secured Overnight Financing Rate (SOFR) Overnight Index Swap Rate | Maximum | Unsecured Notes Two | Revolving Credit Facility
Debt Instrument [Line Items]
Debt to total capital ratio		0.30
Secured Overnight Financing Rate (SOFR) Overnight Index Swap Rate | Maximum | Unsecured debt | Notes payable | Level 2 | Unsecured Notes Two
Debt Instrument [Line Items]
Basis spread on variable rate			1.50%