Investment Securities (Details) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2023	Dec. 31, 2022
Cost
Equity	$ 336,686	$ 323,907
Debt	888,899	833,035
Other	7,040	10,445
Total	1,232,625	1,167,387
Gains
Equity	188,411	159,445
Debt	686	372
Other	29	20
Total	189,126	159,837
Losses
Equity	(7,128)	(8,949)
Debt	(46,470)	(46,369)
Other	(21)	(9)
Total	(53,619)	(55,327)
Fair Value
Equity	517,969	474,403
Debt	843,115	787,038
Other	7,048	10,456
Total	$ 1,368,132	$ 1,271,897