Loan Servicing Rights - Additional Information (Detail) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
Sep. 30, 2018	Dec. 31, 2017	Sep. 30, 2017
Transfers And Servicing [Abstract]
Loan servicing rights	$ 24,336	$ 24,661	$ 24,900
Principal balance of loans serviced for others	3,314,000	3,321,000
Funds held in escrow	$ 43,100	8,900
Percentage of mortgage loan	99.70%
Fair value of servicing rights	$ 27,400	$ 25,800
Fair value at discount rate	12.00%	13.00%
Fair value inputs weighted average prepayment speed	115.00%	140.00%

Fair value inputs discount rate 1.

No definition available.

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- Definition

Weighted average prepayment speed percentage used to find the present value of an amount to be received in the future as an input to measure fair value.

+ References

No definition available.

+ Details

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- Definition

Percentage of loan servicing rights that are mortgage loans.

+ References

No definition available.

+ Details

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- Definition

The principal balance of the loans serviced for others related to the Company's loan servicing rights.

+ References

No definition available.

+ Details

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- Definition

The designation of funds furnished by a borrower to a lender to assure future payments of the borrower's real estate taxes and insurance obligations with respect to a mortgaged property. Escrow deposits may be made for a variety of other purposes such as earnest money and contingent payments. This element excludes replacement reserves which are an escrow separately provided for within the US GAAP taxonomy.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03.10)
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

+ Details

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- Definition

Aggregate amount of servicing assets that are subsequently measured at fair value and servicing assets that are subsequently measured using the amortization method.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 50
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=6469459&loc=d3e122501-111745

+ Details

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- Definition

Fair value of an asset representing net future revenue from contractually specified servicing fees, late charges, and other ancillary revenues, in excess of future costs related to servicing arrangements.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 50
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=6469459&loc=d3e122501-111745

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 50
-Section 50
-Paragraph 3
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=68078379&loc=d3e122625-111746

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- References

No definition available.

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