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Securities, at Fair Value - Narrative (Details) - USD ($)			3 Months Ended	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Mar. 31, 2020	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020	Sep. 30, 2022	Jun. 30, 2022	Mar. 31, 2022	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021
Debt Securities, Available-for-sale [Line Items]
Allowance for credit loss	$ 35,314,000	$ 39,447,000		$ 35,314,000	$ 39,447,000	$ 86,833,000	$ 37,192,000	$ 36,927,000	$ 35,457,000	$ 44,102,000	$ 54,261,000	$ 63,244,000
Impairment and other net (loss)/gain on securities and other portfolio investments				25,067,000	(74,496,000)	$ 350,567,000
Term Notes backed by MSR Related Collateral
Debt Securities, Available-for-sale [Line Items]
Securities, at fair value	97,900,000	153,800,000		97,900,000	153,800,000
Amortized costs	86,400,000	121,400,000		86,400,000	121,400,000
Gross unrealized gains	$ 11,500,000	$ 32,400,000		11,500,000	$ 32,400,000
Weighted average yield	14.30%	10.30%
Weighted average to maturity	9 months 18 days	1 year 8 months 12 days
Impairment			$ 280,800,000
Non-Agency MBS
Debt Securities, Available-for-sale [Line Items]
Gross unrealized losses	$ 0			0
Allowance for credit loss	$ 0			$ 0
MBS and MSR-Related Assets
Debt Securities, Available-for-sale [Line Items]
Impairment and other net (loss)/gain on securities and other portfolio investments			$ 63,500,000

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Financial Instruments, Owned, Mortgages, Mortgage-Backed And Asset-Backed Securities, Amortized Costs

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Financial Instruments, Owned, Mortgages, Mortgage-Backed And Asset-Backed Securities, Gross Unrealized Gains

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Financial Instruments, Owned, Mortgages, Mortgage-Backed And Asset-Backed Securities, Impairment

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Financial Instruments, Owned, Mortgages, Mortgage-Backed And Asset-Backed Securities, Weighted Average To Maturity

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Financial Instruments, Owned, Mortgages, Mortgage-Backed And Asset-Backed Securities, Weighted Average Yield

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Impairment and Other Losses (Gains) On Securities Available-For-Sale And Other Assets

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Amount, before tax, of unrealized loss in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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The fair value as of the balance sheet date of firm holdings in mortgages, mortgage backed securities (investment instruments that represent ownership of an undivided interest in a group of mortgages, where principal and interest from the individual mortgages are used to pay investors' principal and interest on the mortgage backed security) and asset-backed securities that are primarily paid from the cash flows of a discrete pool of receivables or other financial assets (such as credit-card receivables), either fixed or revolving, that by their terms convert into cash within a finite time period. Includes both pledged (to counterparties as collateral for financing transactions) and unpledged holdings.

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Amount of allowance for credit loss on financing receivable. Excludes allowance for financing receivable covered under loss sharing agreement.

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