Certain Transfers of Financial Assets Certain Transfers of Financial Assets - Indirect Automobile Loan Key Metrics (Details) - Indirect automobile loan servicing rights - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016
Servicing Assets at Fair Value [Line Items]
Servicing Asset at Fair Value, Amount	$ 7,436	$ 7,579
Composition of Loans Serviced for Others	100.00%	100.00%
Weighted average remaining term (years)	4 years 6 months 3 days	4 years 9 months
Modeled prepayment speed	20.59%	18.95%
Decline in fair value due to a 10% adverse change	$ (192)	$ (190)
Decline in fair value due to a 20% adverse change	(377)	(371)
Decline in fair value due to a 10% adverse change	(69)	(71)
Decline in fair value due to a 20% adverse change	$ (137)	$ (141)
Fixed-rate Indirect Servicing Loan
Servicing Assets at Fair Value [Line Items]
Composition of Loans Serviced for Others	100.00%	100.00%
Adjustable-rate Indirect Servicing Loan
Servicing Assets at Fair Value [Line Items]
Composition of Loans Serviced for Others	0.00%	0.00%
Weighted Average
Servicing Assets at Fair Value [Line Items]
Weighted average discount rate	7.18%	6.94%

Composition of Loans Serviced for Others

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- Definition

The hypothetical financial impact of a 10 percent adverse change of the discount rate on the fair value of transferor's interests in transferred financial assets (including any servicing assets or servicing liabilities) as of the balance sheet date.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 20
-Section 50
-Paragraph 4
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=82924980&loc=d3e107314-111719

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- Definition

The hypothetical financial impact of a 10 percent adverse change of prepayment speed on the fair value of transferor's interests in transferred financial assets (including any servicing assets or servicing liabilities) as of the balance sheet date.

+ References

+ Details

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- Definition

The hypothetical financial impact of a 20 percent adverse change of the discount rate on the fair value of transferor's interests in transferred financial assets (including any servicing assets or servicing liabilities) as of the balance sheet date.

+ References

+ Details

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- Definition

The hypothetical financial impact of a 20 percent adverse change of prepayment speed on the fair value of transferor's interests in transferred financial assets (including any servicing assets or servicing liabilities) as of the balance sheet date.

+ References

+ 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/presentationRef
-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

+ Details

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- Definition

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

+ References

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

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

+ Details

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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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