Allowance for Probable Loan Losses (Impairment By Loan Class) (Details) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Loan loss allowances, impaired financing receivable, evaluated individually or collectively
Loans Individually Evaluated for Impairment, Recorded Investment	$ 43,972	$ 60,448
Loans Individually Evaluated for Impairment, Allowance	3,723	2,206
Loans Collectively Evaluated for Impairment, Recorded Investment	5,891,602	5,890,466
Loans Collectively Evaluated for Impairment, Allowance	58,061	64,782
Commercial
Loan loss allowances, impaired financing receivable, evaluated individually or collectively
Loans Individually Evaluated for Impairment, Recorded Investment	14,858	30,946
Loans Individually Evaluated for Impairment, Allowance	2,347	1,704
Loans Collectively Evaluated for Impairment, Recorded Investment	931,317	935,905
Loans Collectively Evaluated for Impairment, Allowance	23,436	19,727
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	5,965	6,221
Loans Individually Evaluated for Impairment, Allowance	116	100
Loans Collectively Evaluated for Impairment, Recorded Investment	1,702,187	1,643,606
Loans Collectively Evaluated for Impairment, Allowance	10,754	13,820
Commercial Real Estate: Farmland & Commercial
Loan loss allowances, impaired financing receivable, evaluated individually or collectively
Loans Individually Evaluated for Impairment, Recorded Investment	13,640	13,806
Loans Individually Evaluated for Impairment, Allowance	1,260	202
Loans Collectively Evaluated for Impairment, Recorded Investment	1,917,218	1,981,643
Loans Collectively Evaluated for Impairment, Allowance	15,714	19,567
Commercial Real Estate: Multifamily
Loan loss allowances, impaired financing receivable, evaluated individually or collectively
Loans Individually Evaluated for Impairment, Recorded Investment	164	777
Loans Individually Evaluated for Impairment, Allowance		200
Loans Collectively Evaluated for Impairment, Recorded Investment	148,407	138,671
Loans Collectively Evaluated for Impairment, Allowance	910	1,048
Residential First Lien
Loan loss allowances, impaired financing receivable, evaluated individually or collectively
Loans Individually Evaluated for Impairment, Recorded Investment	6,358	5,699
Loans Collectively Evaluated for Impairment, Recorded Investment	405,982	404,545
Loans Collectively Evaluated for Impairment, Allowance	2,369	3,509
Residential Junior Lien
Loan loss allowances, impaired financing receivable, evaluated individually or collectively
Loans Individually Evaluated for Impairment, Recorded Investment	1,032	950
Loans Collectively Evaluated for Impairment, Recorded Investment	555,840	551,388
Loans Collectively Evaluated for Impairment, Allowance	3,420	5,321
Consumer
Loan loss allowances, impaired financing receivable, evaluated individually or collectively
Loans Individually Evaluated for Impairment, Recorded Investment	1,210	1,297
Loans Collectively Evaluated for Impairment, Recorded Investment	54,715	56,447
Loans Collectively Evaluated for Impairment, Allowance	530	638
Foreign
Loan loss allowances, impaired financing receivable, evaluated individually or collectively
Loans Individually Evaluated for Impairment, Recorded Investment	745	752
Loans Collectively Evaluated for Impairment, Recorded Investment	175,936	178,261
Loans Collectively Evaluated for Impairment, Allowance	$ 928	$ 1,152

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=49124121&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://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=49124121&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=49124121&loc=SL6953423-111524

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