Mortgage Servicing Rights - Value Assumptions (Details)	3 Months Ended	12 Months Ended
Mar. 31, 2018	Dec. 31, 2017
Servicing Assets at Fair Value [Line Items]
Constant prepayment rate	8.20%	9.00%
Discount rate	9.73%	9.45%
Mortgage servicing rights
Servicing Assets at Fair Value [Line Items]
Constant prepayment rate	8.20%	9.00%
Discount rate	9.73%	9.45%

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

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-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

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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