Allowance for Probable Loan Losses (Impairment By Loan Class) (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Loan loss allowances, impaired financing receivable, evaluated individually or collectively
Loans Individually Evaluated for Impairment, Recorded Investment	$ 19,989	$ 23,900
Loans Individually Evaluated for Impairment, Allowance	511	772
Loans Collectively Evaluated for Impairment, Recorded Investment	6,875,153	6,537,389
Loans Collectively Evaluated for Impairment, Allowance	59,349	60,612
Commercial
Loan loss allowances, impaired financing receivable, evaluated individually or collectively
Loans Individually Evaluated for Impairment, Recorded Investment	7,412	9,179
Loans Individually Evaluated for Impairment, Allowance	395	656
Loans Collectively Evaluated for Impairment, Recorded Investment	1,288,324	1,119,790
Loans Collectively Evaluated for Impairment, Allowance	10,576	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	1,794	2,092
Loans Individually Evaluated for Impairment, Allowance	116	116
Loans Collectively Evaluated for Impairment, Recorded Investment	2,042,616	1,884,139
Loans Collectively Evaluated for Impairment, Allowance	16,734	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	1,740	3,509
Loans Collectively Evaluated for Impairment, Recorded Investment	1,965,371	1,946,389
Loans Collectively Evaluated for Impairment, Allowance	16,801	19,353
Commercial Real Estate: Multifamily
Loan loss allowances, impaired financing receivable, evaluated individually or collectively
Loans Individually Evaluated for Impairment, Recorded Investment	649	507
Loans Collectively Evaluated for Impairment, Recorded Investment	241,440	225,750
Loans Collectively Evaluated for Impairment, Allowance	2,199	1,808
Residential First Lien
Loan loss allowances, impaired financing receivable, evaluated individually or collectively
Loans Individually Evaluated for Impairment, Recorded Investment	6,286	6,244
Loans Collectively Evaluated for Impairment, Recorded Investment	432,186	439,556
Loans Collectively Evaluated for Impairment, Allowance	3,729	3,467
Residential Junior Lien
Loan loss allowances, impaired financing receivable, evaluated individually or collectively
Loans Individually Evaluated for Impairment, Recorded Investment	704	901
Loans Collectively Evaluated for Impairment, Recorded Investment	712,588	726,400
Loans Collectively Evaluated for Impairment, Allowance	8,015	7,719
Consumer
Loan loss allowances, impaired financing receivable, evaluated individually or collectively
Loans Individually Evaluated for Impairment, Recorded Investment	1,131	1,175
Loans Collectively Evaluated for Impairment, Recorded Investment	45,941	45,141
Loans Collectively Evaluated for Impairment, Allowance	476	447
Foreign
Loan loss allowances, impaired financing receivable, evaluated individually or collectively
Loans Individually Evaluated for Impairment, Recorded Investment	273	293
Loans Collectively Evaluated for Impairment, Recorded Investment	146,687	150,224
Loans Collectively Evaluated for Impairment, Allowance	$ 819	$ 871

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

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=118936363&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.

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The balance of financing receivables 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 (h)
-URI http://asc.fasb.org/extlink&oid=118936363&loc=SL6953423-111524

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The balance of financing receivables that were individually evaluated for impairment.

+ References

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 11B
-Subparagraph (h)
-URI http://asc.fasb.org/extlink&oid=118936363&loc=SL6953423-111524

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