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Condensed Financial Information of Registrant Condensed Financial Information of Registrant (Narratives) (Details)			3 Months Ended	12 Months Ended
	Nov. 18, 2022 USD ($)	Mar. 08, 2017 USD ($)	Feb. 14, 2023 USD ($)	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)	Mar. 31, 2021 USD ($)	Mar. 29, 2017 USD ($)
Condensed Financial Statements, Captions [Line Items]
Capital distribution from subsidiaries				$ 2,900,000	$ 5,200,000	$ 12,100,000
Proceeds from dividends received				0	191,000,000	121,000,000
Payments of ordinary dividends				0	191,000,000	121,000,000
Revolving Credit Facility
Condensed Financial Statements, Captions [Line Items]
Repayments of debt		$ 320,000,000
Revolving Credit Facility | Unsecured Notes Two
Condensed Financial Statements, Captions [Line Items]
Loan maximum borrowing capacity	$ 200,000,000						$ 75,000,000	$ 50,000,000
Undrawn portion of credit facility				175,000,000
Drawn down amount under credit facility				25,000,000
Revolving Credit Facility | Unsecured Notes Two | Subsequent Event
Condensed Financial Statements, Captions [Line Items]
Interest rate, effective percentage			5.68%
Drawn down amount under credit facility			$ 25,000,000
Unsecured notes | Unsecured Notes One
Condensed Financial Statements, Captions [Line Items]
Interest rate, stated percentage		4.40%
Debt issuance costs		$ 3,400,000
Discount percent		99.847%
Interest rate, effective percentage		4.45%
Unsecured notes | Unsecured Notes One | Notes payable
Condensed Financial Statements, Captions [Line Items]
Unsecured debt		$ 375,000,000		$ 375,000,000	375,000,000
Interest rate, stated percentage				4.40%
Unsecured notes | Unsecured Notes Two | Notes payable
Condensed Financial Statements, Captions [Line Items]
Unsecured debt				$ 25,000,000	0
Minimum | Revolving Credit Facility | Unsecured Notes Two
Condensed Financial Statements, Captions [Line Items]
Commitment fee on undrawn portion of facility	0.125%			0.15%
Minimum | Revolving Credit Facility | Unsecured Notes Two | Secured Overnight Financing Rate (SOFR) Overnight Index Swap Rate
Condensed Financial Statements, Captions [Line Items]
Debt to total capital ratio	0.30
Minimum | Unsecured notes | Unsecured Notes Two | Secured Overnight Financing Rate (SOFR) Overnight Index Swap Rate | Notes payable
Condensed Financial Statements, Captions [Line Items]
Basis spread on variable rate	1.125%
Maximum | Revolving Credit Facility | Unsecured Notes Two
Condensed Financial Statements, Captions [Line Items]
Debt to total capital ratio				0.208
Commitment fee on undrawn portion of facility	0.225%
Maximum | Revolving Credit Facility | Unsecured Notes Two | Secured Overnight Financing Rate (SOFR) Overnight Index Swap Rate
Condensed Financial Statements, Captions [Line Items]
Debt to total capital ratio	0.20
Maximum | Unsecured notes | Unsecured Notes Two | Secured Overnight Financing Rate (SOFR) Overnight Index Swap Rate | Notes payable
Condensed Financial Statements, Captions [Line Items]
Basis spread on variable rate	1.50%
Parent Company
Condensed Financial Statements, Captions [Line Items]
Capital distribution from subsidiaries				$ 3,431,433	0	0
Payments for contributions to subsidiaries				$ 0	$ 0	$ 30,000,000

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