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

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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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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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Amount of restricted 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 other-than-temporary impairment (OTTI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), recognized in earnings.

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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)	3 Months Ended		9 Months Ended
	Sep. 30, 2019 USD ($) investment	Sep. 30, 2018 USD ($)	Sep. 30, 2019 USD ($) investment	Sep. 30, 2018 USD ($)	Dec. 31, 2018 USD ($) investment
Investment Holdings [Line Items]
Trading securities	$ 1,013,785,000		$ 1,013,785,000		$ 1,118,612,000
Trading securities acquired	66,000,000	$ 189,000,000	335,000,000	$ 567,000,000
Trading securities sold	236,000,000	79,000,000	397,000,000	323,000,000
Increase (decrease) in valuation of trading securities	15,000,000	6,000,000	56,000,000	2,000,000
Available-for-sale securities purchased	12,000,000	1,000,000	21,000,000	7,000,000
Available-for-sale securities sold	15,000,000	26,000,000	82,000,000	118,000,000
Net realized gains on AFS securities	$ 4,000,000	$ 7,000,000	$ 13,000,000	$ 21,000,000
Number of AFS securities (in investments) \| investment	113		113		128
Number of securities in unrealized loss position \| investment	1		1		7
Number of securities in a continuous unrealized loss position for twelve consecutive months or longer (in investments) \| investment	1		1		3
Reclassification out of Accumulated Other Comprehensive Income \| Net Unrealized Gains on Available-for-Sale Securities
Investment Holdings [Line Items]
Other than temporary impairment	$ 0		$ 0
Subordinate
Investment Holdings [Line Items]
Trading securities	864,000,000		864,000,000		$ 960,000,000
Interest Only Senior Trading Securities
Investment Holdings [Line Items]
Debt securities, trading	58,000,000		58,000,000		82,000,000
Unpaid principal balance	88,000,000		88,000,000		78,000,000
Certificated Servicing Strips
Investment Holdings [Line Items]
Debt securities, trading	29,000,000		29,000,000		43,000,000
Residential
Investment Holdings [Line Items]
Securities pledged as collateral	736,000,000		736,000,000		844,000,000
Marketable securities, due from five to ten years	8,000,000		8,000,000
Residential Subordinate Securities \| Trading securities
Investment Holdings [Line Items]
Unpaid principal balance	1,010,000,000.00		1,010,000,000.00		1,120,000,000
Subordinate \| Credit Risk Transfer (CRT) Securities
Investment Holdings [Line Items]
Trading securities	128,000,000		128,000,000		277,000,000
Subordinate \| Sequoia securities
Investment Holdings [Line Items]
Trading securities	65,000,000		65,000,000		68,000,000
Subordinate \| Other Third Party Securities
Investment Holdings [Line Items]
Trading securities	207,000,000		207,000,000		186,000,000
Subordinate \| Third Party Multifamily Mortgage-backed Securities
Investment Holdings [Line Items]
Trading securities	464,000,000		464,000,000		429,000,000
Sequoia Choice
Investment Holdings [Line Items]
Trading securities pledged as collateral					130,000,000
Freddie Mac SLST
Investment Holdings [Line Items]
Trading securities pledged as collateral					229,000,000
Freddie Mac K-Series
Investment Holdings [Line Items]
Trading securities pledged as collateral					$ 18,000,000
Short Term Borrowing Agreement
Investment Holdings [Line Items]
Trading securities pledged as collateral	677,000,000		677,000,000
Short Term Borrowing Agreement \| AFS securities retained, at fair value \| Residential
Investment Holdings [Line Items]
Securities pledged as collateral	59,000,000		59,000,000
Short Term Borrowing Agreement \| Sequoia Choice \| Sequoia securities
Investment Holdings [Line Items]
Trading securities pledged as collateral	113,000,000		113,000,000
Short Term Borrowing Agreement \| Freddie Mac SLST \| Sequoia securities
Investment Holdings [Line Items]
Trading securities pledged as collateral	385,000,000		385,000,000
Short Term Borrowing Agreement \| Freddie Mac K-Series \| Sequoia securities
Investment Holdings [Line Items]
Trading securities pledged as collateral	209,000,000		209,000,000
Subordinate Securities Financing Facility
Investment Holdings [Line Items]
Trading securities pledged as collateral	4,000,000		4,000,000
Subordinate Securities Financing Facility \| AFS securities retained, at fair value \| Residential
Investment Holdings [Line Items]
Securities pledged as collateral	123,000,000		123,000,000
Subordinate Securities Financing Facility \| Sequoia Choice \| Sequoia securities
Investment Holdings [Line Items]
Trading securities pledged as collateral	126,000,000		126,000,000
Borrowing Agreement With FHLBC
Investment Holdings [Line Items]
Trading securities pledged as collateral	$ 41,000,000		$ 41,000,000