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Allowance for Probable Loan Losses (Impairment By Loan Class) (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Loan loss allowances, impaired financing receivable, evaluated individually or collectively
Loans Individually Evaluated for Impairment, Recorded Investment	$ 56,049	$ 23,900
Loans Individually Evaluated for Impairment, Allowance	10,282	772
Loans Collectively Evaluated for Impairment, Recorded Investment	6,651,294	6,537,389
Loans Collectively Evaluated for Impairment, Allowance	56,748	60,612
Commercial
Loan loss allowances, impaired financing receivable, evaluated individually or collectively
Loans Individually Evaluated for Impairment, Recorded Investment	18,608	9,179
Loans Individually Evaluated for Impairment, Allowance	666	656
Loans Collectively Evaluated for Impairment, Recorded Investment	1,194,931	1,119,790
Loans Collectively Evaluated for Impairment, Allowance	10,746	11,940
Commercial Real Estate:Other Construction and Land Development
Loan loss allowances, impaired financing receivable, evaluated individually or collectively
Loans Individually Evaluated for Impairment, Recorded Investment	2,059	2,092
Loans Individually Evaluated for Impairment, Allowance	116	116
Loans Collectively Evaluated for Impairment, Recorded Investment	1,932,287	1,884,139
Loans Collectively Evaluated for Impairment, Allowance	14,673	15,007
Commercial Real Estate: Farmland and Commercial
Loan loss allowances, impaired financing receivable, evaluated individually or collectively
Loans Individually Evaluated for Impairment, Recorded Investment	26,391	3,509
Loans Individually Evaluated for Impairment, Allowance	9,500
Loans Collectively Evaluated for Impairment, Recorded Investment	1,870,267	1,946,389
Loans Collectively Evaluated for Impairment, Allowance	16,380	19,353
Commercial Real Estate: Multifamily
Loan loss allowances, impaired financing receivable, evaluated individually or collectively
Loans Individually Evaluated for Impairment, Recorded Investment	507	507
Loans Collectively Evaluated for Impairment, Recorded Investment	293,605	225,750
Loans Collectively Evaluated for Impairment, Allowance	2,345	1,808
Residential First Lien
Loan loss allowances, impaired financing receivable, evaluated individually or collectively
Loans Individually Evaluated for Impairment, Recorded Investment	6,216	6,244
Loans Collectively Evaluated for Impairment, Recorded Investment	450,698	439,556
Loans Collectively Evaluated for Impairment, Allowance	3,546	3,467
Residential Junior Lien
Loan loss allowances, impaired financing receivable, evaluated individually or collectively
Loans Individually Evaluated for Impairment, Recorded Investment	908	901
Loans Collectively Evaluated for Impairment, Recorded Investment	720,204	726,400
Loans Collectively Evaluated for Impairment, Allowance	7,745	7,719
Consumer
Loan loss allowances, impaired financing receivable, evaluated individually or collectively
Loans Individually Evaluated for Impairment, Recorded Investment	1,074	1,175
Loans Collectively Evaluated for Impairment, Recorded Investment	44,999	45,141
Loans Collectively Evaluated for Impairment, Allowance	462	447
Foreign
Loan loss allowances, impaired financing receivable, evaluated individually or collectively
Loans Individually Evaluated for Impairment, Recorded Investment	286	293
Loans Collectively Evaluated for Impairment, Recorded Investment	144,303	150,224
Loans Collectively Evaluated for Impairment, Allowance	$ 851	$ 871

X

- Definition

The valuation allowance for financing receivables that are expected to be uncollectible that were collectively evaluated for impairment.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 11B
-Subparagraph (g)
-URI http://asc.fasb.org/extlink&oid=84173941&loc=SL6953423-111524

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- Definition

Amount of valuation allowance for financing receivables that are expected to be uncollectible that were individually evaluated for impairment.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 11B
-Subparagraph (g)
-URI http://asc.fasb.org/extlink&oid=84173941&loc=SL6953423-111524

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+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 11B
-Subparagraph (h)
-URI http://asc.fasb.org/extlink&oid=84173941&loc=SL6953423-111524

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+ References

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 11B
-Subparagraph (h)
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