Investment in Securities (Proceeds, Realized Gains (Losses) on Sales) (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Securities, Available-for-sale [Line Items]
Available-for-sale securities Realizes Losses - adjustments to cost basis of certain securities	$ (12,000,000.0)	$ (2,000,000.0)	$ (20,400,000)	$ (4,500,000)
Agency RMBS
Securities, Available-for-sale [Line Items]
Proceeds from Sale and Maturity of Debt Securities, Available-for-Sale	86,936,000	311,908,000	474,962,000	878,629,000
Debt Securities, Available-for-Sale, Realized Gain	172,000	728,000	1,023,000	1,923,000
Debt Securities, Available-for-Sale, Realized Loss	(5,662,000)	(34,921,000)	(46,505,000)	(68,939,000)
Debt Securities, Available-for-Sale, Realized Gain (Loss)	(5,490,000)	(34,193,000)	(45,482,000)	(67,016,000)
Non-Agency RMBS and CMBS
Securities, Available-for-sale [Line Items]
Proceeds from Sale and Maturity of Debt Securities, Available-for-Sale	5,012,000	13,121,000	46,243,000	20,715,000
Debt Securities, Available-for-Sale, Realized Gain	329,000	2,210,000	2,742,000	6,546,000
Debt Securities, Available-for-Sale, Realized Loss	(120,000)	(372,000)	(169,000)	(398,000)
Debt Securities, Available-for-Sale, Realized Gain (Loss)	209,000	1,838,000	2,573,000	6,148,000
CLOs
Securities, Available-for-sale [Line Items]
Proceeds from Sale and Maturity of Debt Securities, Available-for-Sale	0	992,000	0	18,259,000
Debt Securities, Available-for-Sale, Realized Gain	53,000	3,324,000	496,000	7,584,000
Debt Securities, Available-for-Sale, Realized Loss	0	(57,000)	(1,000)	(747,000)
Debt Securities, Available-for-Sale, Realized Gain (Loss)	53,000	3,267,000	495,000	6,837,000
Other Securities
Securities, Available-for-sale [Line Items]
Proceeds from Sale and Maturity of Debt Securities, Available-for-Sale	289,990,000	79,510,000	1,000,184,000	173,437,000
Debt Securities, Available-for-Sale, Realized Gain	1,071,000	636,000	2,893,000	4,301,000
Debt Securities, Available-for-Sale, Realized Loss	(2,827,000)	(366,000)	(6,012,000)	(820,000)
Debt Securities, Available-for-Sale, Realized Gain (Loss)	(1,756,000)	270,000	(3,119,000)	3,481,000
Securities Investment [Member]
Securities, Available-for-sale [Line Items]
Proceeds from Sale and Maturity of Debt Securities, Available-for-Sale	381,938,000	405,531,000	1,521,389,000	1,091,040,000
Debt Securities, Available-for-Sale, Realized Gain	1,625,000	6,898,000	7,154,000	20,354,000
Debt Securities, Available-for-Sale, Realized Loss	(8,609,000)	(35,716,000)	(52,687,000)	(70,904,000)
Debt Securities, Available-for-Sale, Realized Gain (Loss)	$ (6,984,000)	$ (28,818,000)	$ (45,533,000)	$ (50,550,000)