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Number of Securities, Continuous Unrealized Loss Position More Than Twelve Months

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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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Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), with single maturity date and allocated without single maturity date, maturing in sixth fiscal year through tenth fiscal year following latest fiscal year. Excludes interim and annual periods when interim period is reported on rolling approach, from latest statement of financial position date.

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Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), with single maturity date and allocated without single maturity date, maturing in second through fifth fiscal year following latest fiscal year. Excludes interim and annual periods when interim period is reported on rolling approach, from latest statement of financial position date.

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Amount of 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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Amount of allowance for credit loss 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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Amount of realized gain 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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Number of investments in debt securities measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in unrealized loss position, without allowance for credit loss. Includes beneficial interest in securitized financial asset.

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Amount of restricted investment in debt security measured at fair value with change in fair value recognized in net income (trading).

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Amount of increase (decrease) of investment in debt and equity securities, measured at fair value with changes in fair value recognized in net income.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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For investments which are quantified by principal amount, the principle balance held at close of period.

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Amount of cash outflow to acquire 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 cash outflow to acquire securities classified as trading securities and held for investment purposes. Excludes payments for trading securities purchased and held principally for the purpose of selling them in the near term (thus held for only a short period of time).

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Amount of cash inflow from sale of 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 cash inflow associated with the sale of securities classified as trading securities and held for investment purposes. Excludes proceeds from trading securities purchased and held principally for the purpose of selling them in the near term (thus held for only a short period of time).

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Amount of investment in debt security measured at fair value with change in fair value recognized in net income (trading) and investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI).

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Amount of investment in debt security measured at fair value with change in fair value recognized in net income (trading).

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Real Estate Securities - Additional Information (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2020 USD ($) investment	Mar. 31, 2019 USD ($)	Dec. 31, 2019 USD ($) investment
Investment Holdings [Line Items]
Available-for-sale securities	$ 129,243		$ 239,334
Trading securities	164,219		$ 860,540
Trading securities acquired	56,000	$ 154,000
Trading securities sold	619,000	29,000
Increase (decrease) in valuation of trading securities	(263,000)	22,000
Available-for-sale securities purchased	31,000	5,000
Available-for-sale securities sold	46,000	42,000
Net realized gains on AFS securities	$ 4,000	$ 7,000
Number of AFS securities (in investments) \| investment	100		107
Number of securities in unrealized loss position \| investment	57		1
Number of securities in a continuous unrealized loss position for twelve consecutive months or longer (in investments) \| investment	0		1
Gross unrealized losses	$ 24,316		$ 29
CECL credit allowance	1,525		0
Interest Only Senior Trading Securities
Investment Holdings [Line Items]
Debt securities, trading	40,000		64,000
Unpaid principal balance	0		84,000
Certificated Servicing Strips
Investment Holdings [Line Items]
Debt securities, trading	19,000		36,000
Re-preforming Loans Securities [Member]
Investment Holdings [Line Items]
Debt securities, trading	13,000		55,000
Residential
Investment Holdings [Line Items]
Available-for-sale securities	106,000		230,000
AFS securities, contractual maturities	20,000
Marketable securities, due from five to ten years	2,000
CECL credit allowance	37,717		32,940
Third Party Multifamily Mortgage-backed Securities
Investment Holdings [Line Items]
Available-for-sale securities	23,000		9,000
Mezzanine
Investment Holdings [Line Items]
Available-for-sale securities	0		13,687
Gross unrealized losses	0		0
CECL credit allowance	0
Mezzanine \| Subordinate Securities
Investment Holdings [Line Items]
Available-for-sale securities	0		13,687
Trading securities	53,781		538,489
Mezzanine \| Sequoia securities
Investment Holdings [Line Items]
Trading securities	28,000		39,000
Mezzanine \| Re-preforming Loans Securities [Member]
Investment Holdings [Line Items]
Trading securities	5,000		30,000
Mezzanine \| Other Third Party Securities
Investment Holdings [Line Items]
Trading securities	26,000		104,000
Mezzanine \| Third Party Multifamily Mortgage-backed Securities
Investment Holdings [Line Items]
Trading securities	0		395,000
Mezzanine \| Trading securities
Investment Holdings [Line Items]
Unpaid principal balance	69,000		537,000
Residential Subordinate Securities \| Trading securities
Investment Holdings [Line Items]
Unpaid principal balance	283,000		302,000
Subordinate Securities
Investment Holdings [Line Items]
Available-for-sale securities	129,243		199,855
Gross unrealized losses	24,316		0
CECL credit allowance	1,525
Subordinate Securities \| Credit Risk Transfer (CRT) Securities
Investment Holdings [Line Items]
Trading securities	20,000		90,000
Subordinate Securities \| Other Third Party Securities
Investment Holdings [Line Items]
Trading securities	47,000		82,000
Subordinate Securities \| Third Party Multifamily Mortgage-backed Securities
Investment Holdings [Line Items]
Trading securities	44,000		76,000
Subordinate \| Subordinate Securities
Investment Holdings [Line Items]
Available-for-sale securities	129,243		199,855
Trading securities	70,879		171,984
Short Term Borrowing Agreement \| Sequoia Choice \| Sequoia securities
Investment Holdings [Line Items]
Trading securities pledged as collateral	51,026		111,341
Short Term Borrowing Agreement \| Freddie Mac SLST \| Sequoia securities
Investment Holdings [Line Items]
Trading securities pledged as collateral	307,175		381,640
Short Term Borrowing Agreement \| Freddie Mac K-Series \| Sequoia securities
Investment Holdings [Line Items]
Trading securities pledged as collateral	$ 22,785		$ 252,284