Investments in Securities and Fair Value Investments in Securities (Schedule of Cost-method Investments) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Fair​Value​Assets​Measured​On​Nonrecurring​Basis​Reconciliation​Calculation​Roll​Forward [Line Items]
Beginning balance	$ 8,688	$ 8,741
Other than Temporary Impairment Losses, Investments	0	0
Observable Changes	0	0
Purchases and Additional Commitments Paid	1,288	1,543
Sales, Returns of Capital, and Other Reductions	(1,061)	(1,596)
Ending balance	8,915	8,688
Cost-method Investments
Fair​Value​Assets​Measured​On​Nonrecurring​Basis​Reconciliation​Calculation​Roll​Forward [Line Items]
Beginning balance	8,688	8,741
Other than Temporary Impairment Losses, Investments	0	0
Observable Changes	0	0
Purchases and Additional Commitments Paid	1,288	1,543
Sales, Returns of Capital, and Other Reductions	(1,061)	(1,596)
Ending balance	$ 8,915	$ 8,688