Allowance for Probable Loan Losses (Impairment By Loan Class) (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Loan loss allowances, impaired financing receivable, evaluated individually or collectively
Loans Individually Evaluated for Impairment, Recorded Investment	$ 43,370	$ 48,405
Loans Individually Evaluated for Impairment, Allowance	1,628	961
Loans Collectively Evaluated for Impairment, Recorded Investment	6,162,476	5,916,283
Loans Collectively Evaluated for Impairment, Allowance	63,291	63,700
Commercial
Loan loss allowances, impaired financing receivable, evaluated individually or collectively
Loans Individually Evaluated for Impairment, Recorded Investment	21,111	22,412
Loans Individually Evaluated for Impairment, Allowance	436
Loans Collectively Evaluated for Impairment, Recorded Investment	892,992	887,255
Loans Collectively Evaluated for Impairment, Allowance	24,704	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	2,805	4,776
Loans Individually Evaluated for Impairment, Allowance	329	371
Loans Collectively Evaluated for Impairment, Recorded Investment	1,835,469	1,712,099
Loans Collectively Evaluated for Impairment, Allowance	12,920	13,518
Commercial Real Estate: Farmland & Commercial
Loan loss allowances, impaired financing receivable, evaluated individually or collectively
Loans Individually Evaluated for Impairment, Recorded Investment	9,319	10,810
Loans Individually Evaluated for Impairment, Allowance	863	546
Loans Collectively Evaluated for Impairment, Recorded Investment	1,951,041	1,932,260
Loans Collectively Evaluated for Impairment, Allowance	16,609	16,185
Commercial Real Estate: Multifamily
Loan loss allowances, impaired financing receivable, evaluated individually or collectively
Loans Individually Evaluated for Impairment, Recorded Investment	515	552
Loans Collectively Evaluated for Impairment, Recorded Investment	176,078	139,914
Loans Collectively Evaluated for Impairment, Allowance	997	806
Residential First Lien
Loan loss allowances, impaired financing receivable, evaluated individually or collectively
Loans Individually Evaluated for Impairment, Recorded Investment	6,749	6,836
Loans Individually Evaluated for Impairment, Allowance		44
Loans Collectively Evaluated for Impairment, Recorded Investment	413,896	415,068
Loans Collectively Evaluated for Impairment, Allowance	2,314	2,411
Residential Junior Lien
Loan loss allowances, impaired financing receivable, evaluated individually or collectively
Loans Individually Evaluated for Impairment, Recorded Investment	965	978
Loans Collectively Evaluated for Impairment, Recorded Investment	657,155	609,340
Loans Collectively Evaluated for Impairment, Allowance	4,357	3,716
Consumer
Loan loss allowances, impaired financing receivable, evaluated individually or collectively
Loans Individually Evaluated for Impairment, Recorded Investment	1,152	1,295
Loans Collectively Evaluated for Impairment, Recorded Investment	52,381	53,873
Loans Collectively Evaluated for Impairment, Allowance	488	531
Foreign
Loan loss allowances, impaired financing receivable, evaluated individually or collectively
Loans Individually Evaluated for Impairment, Recorded Investment	754	746
Loans Collectively Evaluated for Impairment, Recorded Investment	183,464	166,474
Loans Collectively Evaluated for Impairment, Allowance	$ 902	$ 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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- Definition

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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