Investments in Equity Securities (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Mar. 31, 2023	Sep. 30, 2023	Dec. 31, 2022
Debt Securities, Available-for-sale [Line Items]
Equity securities		$ 1,182,061	$ 1,185,894
Fair Value
Debt Securities, Available-for-sale [Line Items]
Cost		1,065,888	1,115,328
Gross Unrealized, Gains	$ 193,218	212,362
Gross Unrealized, Losses	(122,652)	(96,189)
Equity securities		1,182,061	1,185,894
Fair Value | Common stock
Debt Securities, Available-for-sale [Line Items]
Cost		792,512	855,987
Gross Unrealized, Gains	192,165	209,979
Gross Unrealized, Losses	(65,401)	(41,058)
Equity securities		961,433	982,751
Fair Value | Preferred stocks
Debt Securities, Available-for-sale [Line Items]
Cost		273,376	259,341
Gross Unrealized, Gains	1,053	2,383
Gross Unrealized, Losses	$ (57,251)	(55,131)
Equity securities		220,628	203,143
Carrying Value
Debt Securities, Available-for-sale [Line Items]
Equity securities		1,182,061	1,185,894
Carrying Value | Common stock
Debt Securities, Available-for-sale [Line Items]
Equity securities		961,433	982,751
Carrying Value | Preferred stocks
Debt Securities, Available-for-sale [Line Items]
Equity securities		$ 220,628	$ 203,143