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Fair Value Measurement - Summary of Financial Assets And Liabilities Measured at Fair Value on Recurring Basis (Details) - USD ($) $ in Thousands | Dec. 31, 2017 | Dec. 31, 2016
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Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] |  |
Available-for-sale Securities, Fair Value | $ 583,236 | $ 608,560
Servicing assets, at fair value | 21,400 | 21,091
Derivative assets | 5,981 |
Derivative liabilities | 994 |
U.S. Treasury Notes |  |
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] |  |
Available-for-sale Securities, Fair Value | 14,863 | 14,920
U.S. Government Agencies |  |
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] |  |
Available-for-sale Securities, Fair Value | 52,958 | 58,857
Obligations of States, Municipalities, and Political Subdivisions |  |
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] |  |
Available-for-sale Securities, Fair Value | 33,170 | 16,059
Corporate Securities |  |
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] |  |
Available-for-sale Securities, Fair Value | 29,976 | 17,329
Other Securities |  |
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] |  |
Available-for-sale Securities, Fair Value | 5,284 | 4,847
Fair Value, Measurements, Recurring |  |
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] |  |
Servicing assets, at fair value | 21,400 | 21,091
Derivative assets | 5,981 | 4,317
Derivative liabilities | 994 | 559
Fair Value, Measurements, Recurring | U.S. Treasury Notes |  |
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] |  |
Available-for-sale Securities, Fair Value | 14,863 | 14,920
Fair Value, Measurements, Recurring | U.S. Government Agencies |  |
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] |  |
Available-for-sale Securities, Fair Value | 52,958 | 58,857
Fair Value, Measurements, Recurring | Obligations of States, Municipalities, and Political Subdivisions |  |
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] |  |
Available-for-sale Securities, Fair Value | 33,170 | 16,059
Fair Value, Measurements, Recurring | Mortgage-Backed Securities; Residential | Agency |  |
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] |  |
Available-for-sale Securities, Fair Value | 307,457 | 368,160
Fair Value, Measurements, Recurring | Mortgage-Backed Securities; Residential | Non-Agency |  |
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] |  |
Available-for-sale Securities, Fair Value | 39,514 | 19,933
Fair Value, Measurements, Recurring | Mortgage-Backed Securities; Commercial | Agency |  |
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] |  |
Available-for-sale Securities, Fair Value | 69,043 | 77,403
Fair Value, Measurements, Recurring | Mortgage-Backed Securities; Commercial | Non-Agency |  |
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] |  |
Available-for-sale Securities, Fair Value | 30,971 | 31,052
Fair Value, Measurements, Recurring | Corporate Securities |  |
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] |  |
Available-for-sale Securities, Fair Value | 29,976 | 17,329
Fair Value, Measurements, Recurring | Other Securities |  |
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] |  |
Available-for-sale Securities, Fair Value | 5,284 | 4,847
Fair Value, Measurements, Recurring | Level 1 | U.S. Treasury Notes |  |
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] |  |
Available-for-sale Securities, Fair Value | 14,863 | 14,920
Fair Value, Measurements, Recurring | Level 1 | Other Securities |  |
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] |  |
Available-for-sale Securities, Fair Value | 1,921 | 1,938
Fair Value, Measurements, Recurring | Level 2 |  |
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] |  |
Derivative assets | 5,981 | 4,317
Derivative liabilities | 994 | 559
Fair Value, Measurements, Recurring | Level 2 | U.S. Government Agencies |  |
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] |  |
Available-for-sale Securities, Fair Value | 52,958 | 58,857
Fair Value, Measurements, Recurring | Level 2 | Obligations of States, Municipalities, and Political Subdivisions |  |
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] |  |
Available-for-sale Securities, Fair Value | 32,795 | 15,509
Fair Value, Measurements, Recurring | Level 2 | Mortgage-Backed Securities; Residential | Agency |  |
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] |  |
Available-for-sale Securities, Fair Value | 307,457 | 368,160
Fair Value, Measurements, Recurring | Level 2 | Mortgage-Backed Securities; Residential | Non-Agency |  |
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] |  |
Available-for-sale Securities, Fair Value | 39,514 | 19,933
Fair Value, Measurements, Recurring | Level 2 | Mortgage-Backed Securities; Commercial | Agency |  |
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] |  |
Available-for-sale Securities, Fair Value | 69,043 | 77,403
Fair Value, Measurements, Recurring | Level 2 | Mortgage-Backed Securities; Commercial | Non-Agency |  |
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] |  |
Available-for-sale Securities, Fair Value | 30,971 | 31,052
Fair Value, Measurements, Recurring | Level 2 | Corporate Securities |  |
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] |  |
Available-for-sale Securities, Fair Value | 29,976 | 17,329
Fair Value, Measurements, Recurring | Level 2 | Other Securities |  |
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] |  |
Available-for-sale Securities, Fair Value | 2,686 | 2,379
Fair Value, Measurements, Recurring | Level 3 |  |
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] |  |
Servicing assets, at fair value | 21,400 | 21,091
Fair Value, Measurements, Recurring | Level 3 | Obligations of States, Municipalities, and Political Subdivisions |  |
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] |  |
Available-for-sale Securities, Fair Value | 375 | 550
Fair Value, Measurements, Recurring | Level 3 | Other Securities |  |
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] |  |
Available-for-sale Securities, Fair Value | $ 677 | $ 530

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