Fair Value Measurements (Summarize Changes in Level 3 Assets) (Details) - USD ($)	3 Months Ended	9 Months Ended	12 Months Ended
	Mar. 31, 2023	Sep. 30, 2023	Dec. 31, 2022
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Assets, Impairments			$ 0
Securities transferred into or out of level 3, net	$ 0	$ 0
Level 3
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Assets, beginning balance	17,488,000	17,488,000	20,590,000
Assets, earnings		(500,000)	(6,871,000)
Assets, other comprehensive income		0	0
Assets, Impairments		(7,601,000)
Assets, purchases		0	5,611,000
Assets, (sales)		0	(1,842,000)
Assets, maturities		0	0
Assets. transfers out			0
Securities transferred into or out of level 3, net		0
Assets, ending balance		9,387,000	17,488,000
Level 3 | Equity securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Assets, beginning balance	13,898,000	13,898,000	20,590,000
Assets, earnings		(428,000)	(6,692,000)
Assets, other comprehensive income		0	0
Assets, Impairments		(7,601,000)	0
Assets, purchases		0	925,000
Assets, (sales)		0	(925,000)
Assets, maturities		0	0
Assets. transfers out		0	0
Assets, ending balance		5,869,000	13,898,000
Level 3 | Common stock
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Assets, beginning balance	2,599,000	2,599,000	9,294,000
Assets, earnings		(428,000)	(6,695,000)
Assets, other comprehensive income		0	0
Assets, Impairments		0	0
Assets, purchases		0	0
Assets, (sales)		0	0
Assets, maturities		0	0
Assets. transfers out		0	0
Assets, ending balance		2,171,000	2,599,000
Level 3 | Preferred stocks
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Assets, beginning balance	11,299,000	11,299,000	11,296,000
Assets, earnings		0	3,000
Assets, other comprehensive income		0	0
Assets, Impairments		(7,601,000)	0
Assets, purchases		0	925,000
Assets, (sales)		0	(925,000)
Assets, maturities		0	0
Assets. transfers out		0	0
Assets, ending balance		3,698,000	11,299,000
Level 3 | Arbitrage trading account
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Assets, beginning balance	$ 3,590,000	3,590,000	0
Assets, earnings		(72,000)	(179,000)
Assets, other comprehensive income		0	0
Assets, Impairments		0
Assets, Impairments			0
Assets, purchases		0	4,686,000
Assets, (sales)		0	(917,000)
Assets, maturities		0	0
Assets. transfers out			0
Securities transferred into or out of level 3, net		0
Assets, ending balance		$ 3,518,000	$ 3,590,000