Allowance for Probable Loan Losses (Impairment By Loan Class) (Details) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Loan loss allowances, impaired financing receivable, evaluated individually or collectively
Loans Individually Evaluated for Impairment, Recorded Investment	$ 43,013	$ 48,405
Loans Individually Evaluated for Impairment, Allowance	1,503	961
Loans Collectively Evaluated for Impairment, Recorded Investment	5,966,490	5,916,283
Loans Collectively Evaluated for Impairment, Allowance	62,683	63,700
Commercial
Loan loss allowances, impaired financing receivable, evaluated individually or collectively
Loans Individually Evaluated for Impairment, Recorded Investment	21,336	22,412
Loans Individually Evaluated for Impairment, Allowance	277
Loans Collectively Evaluated for Impairment, Recorded Investment	842,857	887,255
Loans Collectively Evaluated for Impairment, Allowance	25,576	25,649
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	3,587	4,776
Loans Individually Evaluated for Impairment, Allowance	319	371
Loans Collectively Evaluated for Impairment, Recorded Investment	1,774,695	1,712,099
Loans Collectively Evaluated for Impairment, Allowance	13,470	13,518
Commercial Real Estate: Farmland & Commercial
Loan loss allowances, impaired financing receivable, evaluated individually or collectively
Loans Individually Evaluated for Impairment, Recorded Investment	7,997	10,810
Loans Individually Evaluated for Impairment, Allowance	863	546
Loans Collectively Evaluated for Impairment, Recorded Investment	1,949,675	1,932,260
Loans Collectively Evaluated for Impairment, Allowance	15,858	16,185
Commercial Real Estate: Multifamily
Loan loss allowances, impaired financing receivable, evaluated individually or collectively
Loans Individually Evaluated for Impairment, Recorded Investment	532	552
Loans Collectively Evaluated for Impairment, Recorded Investment	144,566	139,914
Loans Collectively Evaluated for Impairment, Allowance	818	806
Residential First Lien
Loan loss allowances, impaired financing receivable, evaluated individually or collectively
Loans Individually Evaluated for Impairment, Recorded Investment	6,590	6,836
Loans Individually Evaluated for Impairment, Allowance	44	44
Loans Collectively Evaluated for Impairment, Recorded Investment	411,944	415,068
Loans Collectively Evaluated for Impairment, Allowance	2,347	2,411
Residential Junior Lien
Loan loss allowances, impaired financing receivable, evaluated individually or collectively
Loans Individually Evaluated for Impairment, Recorded Investment	968	978
Loans Collectively Evaluated for Impairment, Recorded Investment	627,513	609,340
Loans Collectively Evaluated for Impairment, Allowance	3,186	3,716
Consumer
Loan loss allowances, impaired financing receivable, evaluated individually or collectively
Loans Individually Evaluated for Impairment, Recorded Investment	1,246	1,295
Loans Collectively Evaluated for Impairment, Recorded Investment	52,368	53,873
Loans Collectively Evaluated for Impairment, Allowance	504	531
Foreign
Loan loss allowances, impaired financing receivable, evaluated individually or collectively
Loans Individually Evaluated for Impairment, Recorded Investment	757	746
Loans Collectively Evaluated for Impairment, Recorded Investment	162,872	166,474
Loans Collectively Evaluated for Impairment, Allowance	$ 924	$ 884

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

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 11B
-Subparagraph (g)
-URI http://asc.fasb.org/extlink&oid=66008989&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

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

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 11B
-Subparagraph (h)
-URI http://asc.fasb.org/extlink&oid=66008989&loc=SL6953423-111524

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

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 11B
-Subparagraph (h)
-URI http://asc.fasb.org/extlink&oid=66008989&loc=SL6953423-111524

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