Mortgage Servicing Rights - Quantitative Assumptions Used for MSRs (Details)	3 Months Ended	12 Months Ended
Mar. 31, 2019	Dec. 31, 2018
Minimum
Quantitative assumptions used in determining lower of cost or fair value of MSRs
Conditional prepayment rate (as a percent)	8.00%	7.86%
Life (of the MSR)	3 years 2 months 5 days	3 years 5 months 5 days
Weighted-average coupon rate (as a percent)	3.97%	3.97%
Discount rate (as a percent)	10.00%	10.00%
Maximum
Quantitative assumptions used in determining lower of cost or fair value of MSRs
Conditional prepayment rate (as a percent)	20.28%	19.26%
Life (of the MSR)	7 years 6 months 22 days	7 years 8 months 5 days
Weighted-average coupon rate (as a percent)	6.67%	6.70%
Discount rate (as a percent)	10.01%	10.02%
Weighted Average
Quantitative assumptions used in determining lower of cost or fair value of MSRs
Conditional prepayment rate (as a percent)	8.47%	8.31%
Life (of the MSR)	7 years 29 days	7 years 2 months 9 days
Weighted-average coupon rate (as a percent)	4.02%	4.02%
Discount rate (as a percent)	10.00%	10.00%

Weighted average coupon rate used to estimate the fair value of servicing assets and servicing liabilities.

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=68078379&loc=d3e122596-111746

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- Definition

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

+ References

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- Definition

Weighted average life of financial assets and financial liabilities, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ 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.

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