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Fair Value Measurement - Summary of Financial Assets Measured at Fair Value on Recurring Basis Using Significant Unobservable Inputs (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Investment Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Balance, beginning of period	$ 1,080
Acquired at fair value		$ 548
Additions, net		550
Maturities	(175)
Amortization	5
Change in unrealized loss	142	(18)
Balance, end of period	1,052	1,080
Servicing Assets
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Balance, beginning of period	21,091
Acquired at fair value		20,295
Additions, net	6,250	539
Change in fair value	(5,941)	257
Balance, end of period	$ 21,400	$ 21,091

X

- Definition

Fair value measurement with unobservable inputs reconciliation recurring basis asset acquired at fair value.

+ References

No definition available.

+ Details

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- Definition

Fair value, measurement with unobservable inputs reconciliation, recurring basis, asset, amortization.

+ References

No definition available.

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- Definition

fair value, measurement with unobservable inputs reconciliation, recurring basis, asset, change in unrealized loss.

+ References

No definition available.

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- Definition

Fair value measurement with unobservable inputs reconciliation recurring basis asset maturities.

+ 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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- Definition

Amount of gain (loss) recognized in the income statement for financial instrument classified as an 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 (c)(1)
-URI http://asc.fasb.org/extlink&oid=66048111&loc=d3e19207-110258

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- Definition

Amount of purchases of financial instrument classified as an 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 (c)(2)
-URI http://asc.fasb.org/extlink&oid=66048111&loc=d3e19207-110258

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- Definition

Fair value of financial instrument classified as an 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 (c)
-URI http://asc.fasb.org/extlink&oid=66048111&loc=d3e19207-110258

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