Loans (Analysis of Loan Portfolio by Major Types of Loans) (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Financing Receivable, Credit Quality Indicator - narrative [Line Items]
Total loans, net of unearned income	$ 9,427,660	$ 8,743,465
Allowance for Credit Loss	(149,140)	(83,968)	$ (83,369)	$ (75,646)
Total loans, net	9,278,520	8,659,497
Commercial Real Estate
Financing Receivable, Credit Quality Indicator - narrative [Line Items]
Total loans, net of unearned income	4,062,313	3,945,853
Allowance for Credit Loss	(68,934)	(20,340)	(14,864)	(16,260)
Commercial Business
Financing Receivable, Credit Quality Indicator - narrative [Line Items]
Total loans, net of unearned income	3,597,968	2,989,613
Allowance for Credit Loss	(45,250)	(30,292)	(34,658)	(25,101)
Agriculture
Financing Receivable, Credit Quality Indicator - narrative [Line Items]
Total loans, net of unearned income	779,627	765,371
Allowance for Credit Loss	(9,052)	(15,835)	(9,589)	(9,662)
Construction
Financing Receivable, Credit Quality Indicator - narrative [Line Items]
Total loans, net of unearned income	268,663	361,533
Allowance for Credit Loss	(7,636)	(8,571)	(14,395)	(15,092)
Real estate: One-to-four family residential
Financing Receivable, Credit Quality Indicator - narrative [Line Items]
Total loans, net of unearned income	683,570	637,325
Allowance for Credit Loss	(16,875)	(7,435)	(8,024)	(8,904)
Consumer Loan
Financing Receivable, Credit Quality Indicator - narrative [Line Items]
Total loans, net of unearned income	35,519	43,770
Allowance for Credit Loss	$ (1,393)	$ (883)	$ (786)	$ (627)