Mortgage Servicing Assets - Schedule of Range and Weighted-Average of Significant Unobservable Inputs (Details) - Discounted Cash Flow [Member] - USD ($)	3 Months Ended
Mar. 31, 2020	Mar. 31, 2019
Commercial Mortgage Backed Securities [Member] \| Minimum [Member]
Servicing Assets at Fair Value [Line Items]
Expected defaults	0.97%	1.00%
Residual cash flows discount rate	7.00%	7.00%
Escrow earn rate	1.20%	2.22%
Loan assumption rate	0.01%	0.00%
Commercial Mortgage Backed Securities [Member] \| Maximum [Member]
Servicing Assets at Fair Value [Line Items]
Expected defaults	2.00%	2.00%
Residual cash flows discount rate	11.42%	15.00%
Escrow earn rate	1.92%	3.70%
Loan assumption rate	3.37%	3.18%
Commercial Mortgage Backed Securities [Member] \| Weighted Average [Member]
Servicing Assets at Fair Value [Line Items]
Expected defaults	1.14%	1.14%
Residual cash flows discount rate	9.24%	9.19%
Escrow earn rate	1.67%	2.98%
Loan assumption rate	1.32%	1.39%
Residential Mortgage Backed Securities [Member] \| Minimum [Member]
Servicing Assets at Fair Value [Line Items]
Expected defaults	7.50%	7.50%
Prepayment speed	10.50%	9.32%
Servicing cost	$ 62,000,000	$ 62,000,000
Residential Mortgage Backed Securities [Member] \| Maximum [Member]
Servicing Assets at Fair Value [Line Items]
Expected defaults	8.50%	10.00%
Prepayment speed	55.60%	58.76%
Servicing cost	$ 8,375,000,000	$ 4,375,000,000
Residential Mortgage Backed Securities [Member] \| Weighted Average [Member]
Servicing Assets at Fair Value [Line Items]
Expected defaults	7.52%	7.54%
Prepayment speed	17.16%	9.93%
Servicing cost	$ 68,140,000	$ 68,230,000

Interest rate used to account for mortgage loan at fair value upon assumption.

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- Definition

Servicing Assets And Servicing Liabilities At Fair Value, Assumptions Used To Estimate Fair Value, Escrow Earn Rate

+ References

No definition available.

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- Definition

Servicing Assets And Servicing Liabilities At Fair Value, Assumptions Used To Estimate Fair Value, Servicing Cost

+ References

No definition available.

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- Definition

Discount rate used to estimate the fair value of servicing assets and servicing liabilities.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 50
-Section 50
-Paragraph 2
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=116651436&loc=d3e122596-111746

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- Definition

Percentage of contractually collectible principal associated with a financial asset expected not to be collected due to default by the borrower.

+ References

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- Definition

Estimated rate of prepayments of principal on servicing assets and servicing liabilities.

+ References

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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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