Loans and Allowance for Loan Losses Loans and Allowance for Loan Losses, Part III (PCI Loans) (Details) - USD ($)	Mar. 31, 2020	Jan. 01, 2020	Dec. 31, 2019	Mar. 31, 2019	Dec. 31, 2018
Carrying Amount [Abstract]
Allowance for loan losses	$ (32,876,000)	$ (28,583,000)	$ (26,911,000)	$ (26,704,000)	$ (26,189,000)
Carrying amount, net of allowance	2,710,171,000		2,666,616,000
Financial Asset Acquired with Credit Deterioration [Member]
Carrying Amount [Abstract]
Carrying amount			4,951,000
Allowance for loan losses		(1,198,000)	(365,000)
Carrying amount, net of allowance			4,586,000
Financing Receivable, Allowance for Credit Losses Reversed			1,229,000
Agricultural loans
Carrying Amount [Abstract]
Allowance for loan losses	(1,064,000)	(1,023,000)	(1,386,000)	(1,130,000)	(951,000)
Agricultural loans | Financial Asset Acquired with Credit Deterioration [Member]
Carrying Amount [Abstract]
Carrying amount			0
Construction and land development
Carrying Amount [Abstract]
Allowance for loan losses	(1,620,000)	(1,033,000)	(1,146,000)	(552,000)	(561,000)
Construction and land development | Financial Asset Acquired with Credit Deterioration [Member]
Carrying Amount [Abstract]
Carrying amount			256,000
Allowance for loan losses		(291,000)	0
Agricultural real estate
Carrying Amount [Abstract]
Allowance for loan losses	(1,335,000)	(1,323,000)	(1,093,000)	(1,282,000)	(1,246,000)
Agricultural real estate | Financial Asset Acquired with Credit Deterioration [Member]
Carrying Amount [Abstract]
Carrying amount			0
1-4 Family residential properties
Carrying Amount [Abstract]
Allowance for loan losses	(1,931,000)	(2,142,000)	(1,386,000)	(1,341,000)	(1,504,000)
1-4 Family residential properties | Financial Asset Acquired with Credit Deterioration [Member]
Carrying Amount [Abstract]
Carrying amount			371,000
Allowance for loan losses		(48,000)	(6,000)
Multifamily residential properties | Financial Asset Acquired with Credit Deterioration [Member]
Carrying Amount [Abstract]
Carrying amount			2,077,000
Commercial real estate | Financial Asset Acquired with Credit Deterioration [Member]
Carrying Amount [Abstract]
Carrying amount			2,247,000
Real Estate Loan [Member] | Financial Asset Acquired with Credit Deterioration [Member]
Carrying Amount [Abstract]
Carrying amount			4,951,000
Commercial and industrial loans
Carrying Amount [Abstract]
Allowance for loan losses		(9,428,000)	(9,273,000)
Commercial and industrial loans | Financial Asset Acquired with Credit Deterioration [Member]
Carrying Amount [Abstract]
Carrying amount			0
Allowance for loan losses		(41,000)	0
Consumer loans
Carrying Amount [Abstract]
Allowance for loan losses	$ (2,011,000)	$ (1,895,000)	(1,429,000)	$ (1,004,000)	$ (932,000)
Consumer loans | Financial Asset Acquired with Credit Deterioration [Member]
Carrying Amount [Abstract]
Carrying amount			$ 0