Fair Value of Financial Instruments - Quantitative Information about Significant Unobservable Inputs Used in Valuation of Level 3 Assets and Liabilities Measured at Fair Value (Details)	12 Months Ended
Dec. 31, 2016 USD ($) $ / loan
Loan purchase commitments
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value	$ 486,000
Loan purchase commitments \| Minimum
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Whole loan spread to TBA price (in dollars per loan) \| $ / loan	2.66
Prepayment rate, percent	15.00%
Whole loan spread to swap rate, percent	2.75%
Whole loan spread to swap rate - hybrid, percent	1.35%
MSR multiple	0.9
Pull-through rate, percent	12.00%
Loan purchase commitments \| Maximum
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Whole loan spread to TBA price (in dollars per loan) \| $ / loan	4.06
Prepayment rate, percent	15.00%
Whole loan spread to swap rate, percent	3.05%
Whole loan spread to swap rate - hybrid, percent	2.75%
MSR multiple	5.4
Pull-through rate, percent	100.00%
Loan purchase commitments \| Weighted Average
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Whole loan spread to TBA price (in dollars per loan) \| $ / loan	3.98
Prepayment rate, percent	15.00%
Whole loan spread to swap rate, percent	3.05%
Whole loan spread to swap rate - hybrid, percent	1.63%
MSR multiple	3.6
Pull-through rate, percent	75.00%
Asset-backed securities issued, net
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value	$ 773,462,000
Asset-backed securities issued, net \| Minimum
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Prepayment rate, percent	1.00%
Loss severity, percent	20.00%
Discount rate, percent	4.00%
Credit support, percent	0.00%
Default rate, percent	1.00%
Asset-backed securities issued, net \| Maximum
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Prepayment rate, percent	20.00%
Loss severity, percent	32.00%
Discount rate, percent	8.00%
Credit support, percent	34.00%
Default rate, percent	12.00%
Asset-backed securities issued, net \| Weighted Average
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Prepayment rate, percent	15.00%
Loss severity, percent	27.00%
Discount rate, percent	5.00%
Credit support, percent	9.00%
Default rate, percent	7.00%
Jumbo fixed rate loans
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value	$ 2,871,120,000
Jumbo fixed rate loans \| Minimum
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Whole loan spread to TBA price (in dollars per loan) \| $ / loan	3.05
Whole loan spread to swap rate, percent	2.75%
Jumbo fixed rate loans \| Maximum
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Whole loan spread to TBA price (in dollars per loan) \| $ / loan	4.06
Whole loan spread to swap rate, percent	3.05%
Jumbo fixed rate loans \| Weighted Average
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Whole loan spread to TBA price (in dollars per loan) \| $ / loan	3.94
Whole loan spread to swap rate, percent	3.04%
Jumbo hybrid loans
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value	$ 50,974,000
Jumbo hybrid loans \| Minimum
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Prepayment rate, percent	15.00%
Whole loan spread to swap rate, percent	1.35%
Jumbo hybrid loans \| Maximum
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Prepayment rate, percent	15.00%
Whole loan spread to swap rate, percent	2.75%
Jumbo hybrid loans \| Weighted Average
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Prepayment rate, percent	15.00%
Whole loan spread to swap rate, percent	1.68%
Jumbo loans committed to sell
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value	$ 173,114,000
Jumbo loans committed to sell \| Minimum
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Whole loan committed sales price (in dollars per loan) \| $ / loan	99.98
Jumbo loans committed to sell \| Maximum
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Whole loan committed sales price (in dollars per loan) \| $ / loan	102.06
Jumbo loans committed to sell \| Weighted Average
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Whole loan committed sales price (in dollars per loan) \| $ / loan	100.61
Loans held by consolidated Sequoia entities
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value	$ 791,636,000
Residential loans, at lower of cost or fair value
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value	$ 867,000
Residential loans, at lower of cost or fair value \| Minimum
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Loss severity, percent	15.00%
Residential loans, at lower of cost or fair value \| Maximum
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Loss severity, percent	30.00%
Residential loans, at lower of cost or fair value \| Weighted Average
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Loss severity, percent	20.00%
Trading and AFS securities
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value	$ 1,018,439,000
Trading and AFS securities \| Minimum
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Prepayment rate, percent	1.00%
Loss severity, percent	20.00%
Discount rate, percent	4.00%
Credit support, percent	0.00%
Default rate, percent	0.00%
Trading and AFS securities \| Maximum
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Prepayment rate, percent	57.00%
Loss severity, percent	65.00%
Discount rate, percent	12.00%
Credit support, percent	48.00%
Default rate, percent	35.00%
Trading and AFS securities \| Weighted Average
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Prepayment rate, percent	20.00%
Loss severity, percent	22.00%
Discount rate, percent	7.00%
Credit support, percent	3.00%
Default rate, percent	2.00%
MSRs
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value	$ 118,526,000
MSRs \| Minimum
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Prepayment rate, percent	5.00%
Discount rate, percent	10.00%
Per loan annual cost to service (in dollars per loan)	$ 72
MSRs \| Maximum
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Prepayment rate, percent	11.00%
Discount rate, percent	11.00%
Per loan annual cost to service (in dollars per loan)	$ 82
MSRs \| Weighted Average
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Prepayment rate, percent	9.00%
Discount rate, percent	10.00%
Per loan annual cost to service (in dollars per loan)	$ 77
Guarantee asset
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value	$ 4,092,000
Guarantee asset \| Minimum
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Prepayment rate, percent	10.00%
Discount rate, percent	11.00%
Guarantee asset \| Maximum
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Prepayment rate, percent	10.00%
Discount rate, percent	11.00%
Guarantee asset \| Weighted Average
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Prepayment rate, percent	10.00%
Discount rate, percent	11.00%
REO
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value	$ 5,207,000
REO \| Minimum
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Loss severity, percent	1.00%
REO \| Maximum
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Loss severity, percent	100.00%
REO \| Weighted Average
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Loss severity, percent	24.00%

Fair Value Inputs, Credit Spreads, Hybrid

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- Definition

Percentage of credit support for financial asset.

+ References

No definition available.

+ Details

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- Definition

Fair Value Inputs, Fallout Rate

+ References

No definition available.

+ Details

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- Definition

Fair Value Inputs, Mortgage Servicing Right (MSR) Multiple

+ References

No definition available.

+ Details

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- Definition

Fair Value Inputs, Per Loan Annual Cost To Service

+ References

No definition available.

+ Details

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- Definition

Fair Value Inputs, Whole Loan Committed Sales Price

+ References

No definition available.

+ Details

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- Definition

Fair Value Inputs Whole Loan Credit Spreads

+ References

No definition available.

+ Details

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- Definition

Fair Value Inputs, Whole Loan Spread

+ References

No definition available.

+ Details

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- Definition

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.

+ References

No definition available.

+ Details

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- Definition

Interest rate used to find the present value of an amount to be paid or received in the future as an input to measure fair value. For example, but not limited to, weighted average cost of capital (WACC), cost of capital, cost of equity and cost of debt.

+ References

+ Details

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- Definition

Loss, including interest and principal, incurred on a defaulted security, expressed as a percentage of the original principal balance, used as an input to measure fair value.

+ References

+ Details

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- Definition

Rate at which loans or a loan portfolio are expected to prepay principal balances, used as an input to measure fair value.

+ References

+ Details

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- Definition

Percentage of likelihood a loan will not be repaid and instead default, used as an input to measure fair value.

+ References

+ Details

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- Definition

Fair value of financial instrument classified as derivative asset (liability) after deduction of derivative liability (asset), measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=66048111&loc=d3e19207-110258

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 3
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=66048111&loc=d3e19279-110258

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