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Fair Value Measurements and Fair Value of Financial Instruments, Estimated Fair Values of Financial Instruments (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Financial assets [Abstract]
HTM securities	$ 782,761	$ 778,675
Carrying Amount [Member] | Level 2 [Member]
Financial assets [Abstract]
HTM securities	780,565	783,599
Financial liabilities [Abstract]
Time deposits	922,304	930,678
Long-term debt	73,696	73,724
Junior subordinated debt	101,196	101,196
Carrying Amount [Member] | Level 3 [Member]
Financial assets [Abstract]
Net loans	6,827,432	6,822,147
Estimated Fair Value [Member] | Level 2 [Member]
Financial assets [Abstract]
HTM securities	782,761	778,675
Financial liabilities [Abstract]
Time deposits	915,990	920,534
Long-term debt	73,981	73,927
Junior subordinated debt	102,946	100,114
Estimated Fair Value [Member] | Level 3 [Member]
Financial assets [Abstract]
Net loans	$ 6,775,550	$ 6,754,460

X

- Definition

Fair value portion of time deposit liabilities, including certificates of deposit.

+ References

No definition available.

+ Details

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X

- Definition

Fair value portion of debt instrument payable, including, but not limited to, notes payable and loans payable.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 10
-URI http://asc.fasb.org/extlink&oid=109250915&loc=d3e13433-108611

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X

- Definition

Fair value of subordinated debt obligations including, but not limited to, subordinated loan, subordinated bond, subordinated debenture or junior debt.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=99377789&loc=d3e19207-110258

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
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-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=99377789&loc=d3e19207-110258

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- References

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- Definition

Fair value of investment in debt security measured at amortized cost (held-to-maturity).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 5
-Subparagraph (aa)
-URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27232-111563

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- Definition

Fair value portion of loans held-for-sale including, but not limited to, mortgage loans and finance receivables.

+ References

No definition available.

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