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Allowance for Probable Loan Losses (Portfolio Credit Quality By Loan Class) (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2019 USD ($) item	Dec. 31, 2018 USD ($)
Loan portfolio by credit quality indicator
Portfolio, total	$ 6,894,946	$ 6,561,289
Number of additional relationships reclassified from Pass to Watch List - Substandard | item	2
Pass
Loan portfolio by credit quality indicator
Portfolio, total	$ 6,538,085	6,126,933
Special Review
Loan portfolio by credit quality indicator
Portfolio, total	33,553	64,135
Watch List - Pass
Loan portfolio by credit quality indicator
Portfolio, total	62,315	92,976
Watch List - Substandard
Loan portfolio by credit quality indicator
Portfolio, total	248,318	253,345
Watch - List Impaired
Loan portfolio by credit quality indicator
Portfolio, total	12,675	23,900
Commercial
Loan portfolio by credit quality indicator
Portfolio, total	1,292,660	1,128,969
Commercial | Pass
Loan portfolio by credit quality indicator
Portfolio, total	1,228,110	998,625
Commercial | Special Review
Loan portfolio by credit quality indicator
Portfolio, total	569	441
Commercial | Watch List - Pass
Loan portfolio by credit quality indicator
Portfolio, total	39	44,544
Commercial | Watch List - Substandard
Loan portfolio by credit quality indicator
Portfolio, total	62,007	76,180
Commercial | Watch - List Impaired
Loan portfolio by credit quality indicator
Portfolio, total	1,935	9,179
Commercial Real Estate:Other Construction and Land Development
Loan portfolio by credit quality indicator
Portfolio, total	2,185,883	1,886,231
Commercial Real Estate:Other Construction and Land Development | Pass
Loan portfolio by credit quality indicator
Portfolio, total	2,090,370	1,817,098
Commercial Real Estate:Other Construction and Land Development | Special Review
Loan portfolio by credit quality indicator
Portfolio, total	18,721	1,648
Commercial Real Estate:Other Construction and Land Development | Watch List - Pass
Loan portfolio by credit quality indicator
Portfolio, total	41,949	9,055
Commercial Real Estate:Other Construction and Land Development | Watch List - Substandard
Loan portfolio by credit quality indicator
Portfolio, total	33,905	56,338
Commercial Real Estate:Other Construction and Land Development | Watch - List Impaired
Loan portfolio by credit quality indicator
Portfolio, total	938	2,092
Commercial Real Estate: Farmland and Commercial
Loan portfolio by credit quality indicator
Portfolio, total	1,896,747	1,949,898
Commercial Real Estate: Farmland and Commercial | Pass
Loan portfolio by credit quality indicator
Portfolio, total	1,710,446	1,726,711
Commercial Real Estate: Farmland and Commercial | Special Review
Loan portfolio by credit quality indicator
Portfolio, total	13,184	62,046
Commercial Real Estate: Farmland and Commercial | Watch List - Pass
Loan portfolio by credit quality indicator
Portfolio, total	20,183	38,373
Commercial Real Estate: Farmland and Commercial | Watch List - Substandard
Loan portfolio by credit quality indicator
Portfolio, total	151,726	119,259
Commercial Real Estate: Farmland and Commercial | Watch - List Impaired
Loan portfolio by credit quality indicator
Portfolio, total	1,208	3,509
Commercial Real Estate: Multifamily
Loan portfolio by credit quality indicator
Portfolio, total	190,430	226,257
Commercial Real Estate: Multifamily | Pass
Loan portfolio by credit quality indicator
Portfolio, total	190,265	224,823
Commercial Real Estate: Multifamily | Watch List - Substandard
Loan portfolio by credit quality indicator
Portfolio, total		927
Commercial Real Estate: Multifamily | Watch - List Impaired
Loan portfolio by credit quality indicator
Portfolio, total	165	507
Residential First Lien
Loan portfolio by credit quality indicator
Portfolio, total	433,901	445,800
Residential First Lien | Pass
Loan portfolio by credit quality indicator
Portfolio, total	426,546	438,773
Residential First Lien | Special Review
Loan portfolio by credit quality indicator
Portfolio, total	253
Residential First Lien | Watch List - Pass
Loan portfolio by credit quality indicator
Portfolio, total	144	142
Residential First Lien | Watch List - Substandard
Loan portfolio by credit quality indicator
Portfolio, total	680	641
Residential First Lien | Watch - List Impaired
Loan portfolio by credit quality indicator
Portfolio, total	6,278	6,244
Residential Junior Lien
Loan portfolio by credit quality indicator
Portfolio, total	706,476	727,301
Residential Junior Lien | Pass
Loan portfolio by credit quality indicator
Portfolio, total	704,958	725,538
Residential Junior Lien | Special Review
Loan portfolio by credit quality indicator
Portfolio, total	826
Residential Junior Lien | Watch List - Pass
Loan portfolio by credit quality indicator
Portfolio, total		862
Residential Junior Lien | Watch - List Impaired
Loan portfolio by credit quality indicator
Portfolio, total	692	901
Consumer
Loan portfolio by credit quality indicator
Portfolio, total	47,800	46,316
Consumer | Pass
Loan portfolio by credit quality indicator
Portfolio, total	46,605	45,141
Consumer | Watch - List Impaired
Loan portfolio by credit quality indicator
Portfolio, total	1,195	1,175
Foreign
Loan portfolio by credit quality indicator
Portfolio, total	141,049	150,517
Foreign | Pass
Loan portfolio by credit quality indicator
Portfolio, total	140,785	150,224
Foreign | Watch - List Impaired
Loan portfolio by credit quality indicator
Portfolio, total	$ 264	$ 293

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The number of relationships that were reclassified from pass category to watch list - substandard category.

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Amount before allowance and after deduction of deferred interest and fees, unamortized costs and premiums and discounts from face amounts, of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Excludes loans and leases covered under loss sharing agreements.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=118952595&loc=d3e4428-111522

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=118936363&loc=d3e5074-111524

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