Mortgage-Backed Securities - Investment Type (Details) - USD ($) $ in Thousands		Jun. 30, 2024	Dec. 31, 2023
Debt Securities, Trading and Available-for-sale [Abstract]
Par Value		$ 6,456,137	$ 6,143,945
Amortized Cost		6,568,580	6,283,185
Non-Agency other, Amortized Cost		1,067,477	1,131,769
Fair Value		6,193,139	6,038,948
Gross Unrealized Gain		1,359	1,324
Gross Unrealized Loss		(178,914)	(159,826)
Fair Value		889,922	973,267
Amortized Cost		5,501,103	5,151,416
Gross Unrealized Gain		13,333	48,461
Gross Unrealized Loss		(211,219)	(134,196)
Fair Value		5,303,217	5,065,681
Residential Mortgage Backed Securities [Member] | Agency MBS
Debt Securities, Trading and Available-for-sale [Abstract]
Par Value		6,353,838	6,022,502
Amortized Cost		6,326,070	5,993,922
Non-Agency other, Amortized Cost		863,181	898,420
Fair Value		5,962,418	5,763,532
Gross Unrealized Gain		0	0
Gross Unrealized Loss		(168,488)	(148,606)
Fair Value		694,693	749,814
Amortized Cost		5,462,889	5,095,502
Gross Unrealized Gain		13,333	48,459
Gross Unrealized Loss		(208,497)	(130,243)
Fair Value		5,267,725	5,013,718
Commercial Mortgage Backed Securities [Member] | Agency MBS
Debt Securities, Trading and Available-for-sale [Abstract]
Par Value		102,299	121,293
Amortized Cost		102,516	121,799
Non-Agency other, Amortized Cost		102,516	106,527
Fair Value		97,482	115,595
Gross Unrealized Gain		0	28
Gross Unrealized Loss		(5,034)	(5,159)
Fair Value		97,482	101,396
Amortized Cost			15,272
Gross Unrealized Gain			0
Gross Unrealized Loss			(1,073)
Fair Value			14,199
Interest-Only-Strip [Member]
Debt Securities, Trading and Available-for-sale [Abstract]
Amortized Cost	[1]	139,994	167,314
Non-Agency other, Amortized Cost		101,780	126,672
Fair Value	[1]	133,239	159,718
Gross Unrealized Gain		1,359	1,296
Gross Unrealized Loss		(5,392)	(6,014)
Fair Value		97,747	121,954
Amortized Cost		38,214	40,642
Gross Unrealized Gain		0	2
Gross Unrealized Loss		(2,722)	(2,880)
Fair Value		35,492	37,764
Interest-Only-Strip, Agency CMBS [Member]
Debt Securities, Trading and Available-for-sale [Abstract]
Par Value		7,321,369	7,723,379
Interest-Only-Strip, Non-Agency CMBS [Member]
Debt Securities, Trading and Available-for-sale [Abstract]
Par Value		3,167,395	3,860,007
Non-Agency MBS
Debt Securities, Trading and Available-for-sale [Abstract]
Par Value		0	150
Non-Agency other, Amortized Cost		0	150
Gross Unrealized Gain			0
Gross Unrealized Loss			(47)
Fair Value		$ 0	$ 103

[1] (1) The notional balance for Agency CMBS IO and non-Agency CMBS IO was $7,321,369 and $3,167,395, respectively, as of June 30, 2024, and $7,723,379 and $3,860,007, respectively, as of December 31, 2023.