Investment in Securities (Narrative) (Details) - USD ($)	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Allowance for Credit Loss	$ 16,900,000		$ 16,900,000		$ 24,900,000
Debt Securities, Available-for-sale, Purchased with Credit Deterioration, Allowance for Credit Loss at Acquisition Date			300,000		2,600,000
Available-for-sale securities Realizes Losses - Write offs	(82,000)	$ (13,800,000)	(1,300,000)	$ (13,800,000)
Catch-up premium amortization adjustment	3,000,000.0	(3,600,000)	3,000,000.0	(4,800,000)
Residential mortgage loans | Loans held-for-investment [Member]
Securities, Available-for-sale [Line Items]
Financing Receivable, Allowance for Credit Loss	$ 2,100,000		2,100,000		$ 2,200,000
Realized Losses, Write offs on loans		$ (500,000)	$ (33,000)	$ (500,000)