Investments (Repurchase Agreement and Securities Lending) (Details) - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Total cash collateral for loaned securities	$ 184,001	$ 86,750
Overnight & Continuous
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Total cash collateral for loaned securities	184,001	86,750
Up to 30 Days
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Total cash collateral for loaned securities	0	0
30 to 90 Days
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Total cash collateral for loaned securities	0	0
Foreign government bonds
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Total cash collateral for loaned securities	490	506
Foreign government bonds | Overnight & Continuous
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Total cash collateral for loaned securities	490	506
Foreign government bonds | Up to 30 Days
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Total cash collateral for loaned securities	0	0
U.S. public corporate securities
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Total cash collateral for loaned securities	6,879	7,903
U.S. public corporate securities | Overnight & Continuous
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Total cash collateral for loaned securities	6,879	7,903
U.S. public corporate securities | Up to 30 Days
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Total cash collateral for loaned securities	0	0
Foreign public corporate securities
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Total cash collateral for loaned securities	3,362	12,873
Foreign public corporate securities | Overnight & Continuous
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Total cash collateral for loaned securities	3,362	12,873
Foreign public corporate securities | Up to 30 Days
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Total cash collateral for loaned securities	0	0
Equity securities
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Total cash collateral for loaned securities	173,270	65,468
Equity securities | Overnight & Continuous
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Total cash collateral for loaned securities	173,270	65,468
Equity securities | Up to 30 Days
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Total cash collateral for loaned securities	$ 0	$ 0