Loans - Schedule of Recorded Investment in Criticized Loans by Class and Credit Quality Indicator (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment					$ 8,936,200,000
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	$ 4,300,000		$ 4,300,000		300,000
Impaired Financing Receivable, Recorded Investment	65,900,000		65,900,000		64,700,000
Loans and Leases Receivable, Commitments to Purchase or Sell	0	$ 0	0	$ 0
Proceeds from Sale of Loans Held-for-investment	0	$ 0	0	$ 0
Non-owner occupied
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
2020	413.2		413.2
2019	305.2		305.2
2018	215.8		215.8
2017	113.0		113.0
2016	160.8		160.8
Prior	400.6		400.6
Revolving Loans Amortized Cost Basis	12.8		12.8
Total	1,621.4		1,621.4
Commercial Real Estate
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment					3,487,800,000
Commercial
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment	3,690,900,000		3,690,900,000		3,487,800,000
Land acquisition & development
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
2020	81.8		81.8
2019	71.1		71.1
2018	41.6		41.6
2017	34.1		34.1
2016	9.4		9.4
Prior	30.0		30.0
Revolving Loans Amortized Cost Basis	6.8		6.8
Total	274.8		274.8
Loans held for investment	274,800,000		274,800,000		302,100,000
Residential
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
2020	65.7		65.7
2019	73.3		73.3
2018	16.1		16.1
2017	5.6		5.6
2016	0.3		0.3
Prior	0.1		0.1
Revolving Loans Amortized Cost Basis	66.8		66.8
Total	227.9		227.9
Loans held for investment	227,900,000		227,900,000		244,100,000
Commercial
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
2020	188.4		188.4
2019	225.5		225.5
2018	86.1		86.1
2017	12.0		12.0
2016	9.7		9.7
Prior	0.4		0.4
Revolving Loans Amortized Cost Basis	8.7		8.7
Total	530.8		530.8
Loans held for investment	530,800,000		530,800,000		431,500,000
Total construction
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment					977,700,000
Residential
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment	1,311,200,000		1,311,200,000		1,246,100,000
Total construction loans
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment	1,033,500,000		1,033,500,000		977,700,000
Agricultural
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
2020	39.2		39.2
2019	64.5		64.5
2018	35.9		35.9
2017	20.8		20.8
2016	18.7		18.7
Prior	39.5		39.5
Revolving Loans Amortized Cost Basis	9.1		9.1
Total	227.7		227.7
Loans held for investment	227,700,000		227,700,000		226,600,000
Real Estate Loan
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment					5,938,200,000
Total real estate loans
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment	6,263,300,000		6,263,300,000		5,938,200,000
Indirect consumer
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
2020	273.8		273.8
2019	213.1		213.1
2018	134.1		134.1
2017	85.9		85.9
2016	56.9		56.9
Prior	49.0		49.0
Revolving Loans Amortized Cost Basis	0		0
Total	812.8		812.8
Loans held for investment	812,800,000		812,800,000		784,600,000
Direct consumer
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
2020	40.6		40.6
2019	34.1		34.1
2018	34.0		34.0
2017	14.2		14.2
2016	6.5		6.5
Prior	9.8		9.8
Revolving Loans Amortized Cost Basis	22.9		22.9
Total	162.1		162.1
Loans held for investment	162,100,000		162,100,000		179,000,000.0
Credit card
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
2020	140.3		140.3
Loans held for investment	69,900,000		69,900,000		81,600,000
Total consumer loans
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment	1,044,800,000		1,044,800,000		1,045,200,000
Commercial
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment	2,599,600,000		2,599,600,000		1,673,700,000
Agricultural
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment	274,700,000		274,700,000		279,100,000
Owner occupied
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
2020	339.2		339.2
2019	339.7		339.7
2018	241.1		241.1
2017	139.8		139.8
2016	200.2		200.2
Prior	435.4		435.4
Revolving Loans Amortized Cost Basis	14.6		14.6
Total	1,710.0		1,710.0
Multi-family
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
2020	106.0		106.0
2019	63.0		63.0
2018	29.2		29.2
2017	42.4		42.4
2016	26.1		26.1
Prior	90.9		90.9
Revolving Loans Amortized Cost Basis	1.9		1.9
Total	359.5		359.5
Commercial and floor plans
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
2020	1,403.0		1,403.0
2019	182.9		182.9
2018	157.1		157.1
2017	94.1		94.1
2016	57.6		57.6
Prior	106.0		106.0
Revolving Loans Amortized Cost Basis	251.5		251.5
Total	2,252.2		2,252.2
Commercial purpose secured by 1-4 family
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
2020	63.0		63.0
2019	64.6		64.6
2018	43.2		43.2
2017	24.4		24.4
2016	18.7		18.7
Prior	44.7		44.7
Revolving Loans Amortized Cost Basis	20.0		20.0
Total	278.6		278.6
Agriculture Portfolio Segment [Member]
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
2020	48.5		48.5
2019	29.1		29.1
2018	19.0		19.0
2017	7.3		7.3
2016	4.1		4.1
Prior	2.2		2.2
Revolving Loans Amortized Cost Basis	162.9		162.9
Total	273.1		273.1
Loans held for investment					279,100,000
Residential 1-4 family
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
2020	311.1		311.1
2019	120.5		120.5
2018	71.6		71.6
2017	57.9		57.9
2016	76.9		76.9
Prior	271.1		271.1
Revolving Loans Amortized Cost Basis	0		0
Total	909.1		909.1
Consumer Home Equity and HELOC
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
2020	10.3		10.3
2019	8.3		8.3
2018	9.6		9.6
2017	10.8		10.8
2016	5.3		5.3
Prior	17.1		17.1
Revolving Loans Amortized Cost Basis	340.7		340.7
Total	402.1		402.1
Pass
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment					8,548,800,000
Pass | Non-owner occupied
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
2020	397.3		397.3
2019	299.3		299.3
2018	213.8		213.8
2017	108.8		108.8
2016	159.0		159.0
Prior	368.2		368.2
Revolving Loans Amortized Cost Basis	12.8		12.8
Total	1,559.2		1,559.2
Pass | Commercial Real Estate
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment					3,305,000,000.0
Pass | Land acquisition & development
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
2020	81.0		81.0
2019	71.0		71.0
2018	40.4		40.4
2017	33.0		33.0
2016	9.4		9.4
Prior	28.5		28.5
Revolving Loans Amortized Cost Basis	6.1		6.1
Total	269.4		269.4
Loans held for investment					295,400,000
Pass | Residential
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
2020	65.1		65.1
2019	73.3		73.3
2018	14.9		14.9
2017	5.6		5.6
2016	0.3		0.3
Prior	0.1		0.1
Revolving Loans Amortized Cost Basis	66.8		66.8
Total	226.1		226.1
Loans held for investment					241,000,000.0
Pass | Commercial
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
2020	188.4		188.4
2019	223.3		223.3
2018	84.2		84.2
2017	12.0		12.0
2016	9.7		9.7
Prior	0.3		0.3
Revolving Loans Amortized Cost Basis	8.7		8.7
Total	526.6		526.6
Loans held for investment					428,300,000
Pass | Total construction
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment					964,700,000
Pass | Residential
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment					1,235,400,000
Pass | Agricultural
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
2020	35.7		35.7
2019	46.6		46.6
2018	31.2		31.2
2017	18.1		18.1
2016	14.3		14.3
Prior	30.2		30.2
Revolving Loans Amortized Cost Basis	6.4		6.4
Total	182.5		182.5
Loans held for investment					185,700,000
Pass | Real Estate Loan
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment					5,690,800,000
Pass | Indirect consumer
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment					781,500,000
Pass | Direct consumer
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment					177,700,000
Pass | Credit card
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment					81,600,000
Pass | Total consumer loans
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment					1,040,800,000
Pass | Commercial
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment					1,569,400,000
Pass | Owner occupied
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
2020	325.0		325.0
2019	324.4		324.4
2018	220.9		220.9
2017	131.4		131.4
2016	166.3		166.3
Prior	407.1		407.1
Revolving Loans Amortized Cost Basis	13.9		13.9
Total	1,589.0		1,589.0
Pass | Multi-family
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
2020	106.0		106.0
2019	63.0		63.0
2018	29.2		29.2
2017	42.4		42.4
2016	26.1		26.1
Prior	90.8		90.8
Revolving Loans Amortized Cost Basis	1.9		1.9
Total	359.4		359.4
Pass | Commercial and floor plans
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
2020	1,385.9		1,385.9
2019	173.4		173.4
2018	150.5		150.5
2017	86.3		86.3
2016	48.8		48.8
Prior	100.3		100.3
Revolving Loans Amortized Cost Basis	236.6		236.6
Total	2,181.8		2,181.8
Pass | Commercial purpose secured by 1-4 family
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
2020	60.3		60.3
2019	62.9		62.9
2018	38.4		38.4
2017	23.8		23.8
2016	16.7		16.7
Prior	42.4		42.4
Revolving Loans Amortized Cost Basis	19.5		19.5
Total	264.0		264.0
Pass | Agriculture Portfolio Segment [Member]
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
2020	39.5		39.5
2019	26.5		26.5
2018	14.2		14.2
2017	5.7		5.7
2016	3.9		3.9
Prior	1.4		1.4
Revolving Loans Amortized Cost Basis	140.9		140.9
Total	232.1		232.1
Loans held for investment					247,800,000
Other Assets Especially Mentioned
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment					157,500,000
Other Assets Especially Mentioned | Non-owner occupied
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
2020	0		0
2019	3.1		3.1
2018	0.9		0.9
2017	0.1		0.1
2016	0.7		0.7
Prior	17.6		17.6
Revolving Loans Amortized Cost Basis	0		0
Total	22.4		22.4
Other Assets Especially Mentioned | Commercial Real Estate
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment					84,700,000
Other Assets Especially Mentioned | Land acquisition & development
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
2020	0.4		0.4
2019	0.1		0.1
2018	0		0
2017	1.0		1.0
2016	0		0
Prior	1.2		1.2
Revolving Loans Amortized Cost Basis	0.3		0.3
Total	3.0		3.0
Loans held for investment					3,800,000
Other Assets Especially Mentioned | Residential
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
2020	0		0
2019	0		0
2018	0		0
2017	0		0
2016	0		0
Prior	0		0
Revolving Loans Amortized Cost Basis	0		0
Total	0		0
Loans held for investment					900,000
Other Assets Especially Mentioned | Commercial
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
2020	0		0
2019	1.4		1.4
2018	1.5		1.5
2017	0		0
2016	0		0
Prior	0		0
Revolving Loans Amortized Cost Basis	0		0
Total	2.9		2.9
Loans held for investment					1,700,000
Other Assets Especially Mentioned | Total construction
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment					6,400,000
Other Assets Especially Mentioned | Residential
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment					2,600,000
Other Assets Especially Mentioned | Agricultural
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
2020	3.4		3.4
2019	7.6		7.6
2018	1.2		1.2
2017	1.6		1.6
2016	0.9		0.9
Prior	3.9		3.9
Revolving Loans Amortized Cost Basis	0.9		0.9
Total	19.5		19.5
Loans held for investment					14,300,000
Other Assets Especially Mentioned | Real Estate Loan
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment					108,000,000.0
Other Assets Especially Mentioned | Indirect consumer
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment					200,000
Other Assets Especially Mentioned | Direct consumer
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment					400,000
Other Assets Especially Mentioned | Credit card
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment					0
Other Assets Especially Mentioned | Total consumer loans
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment					600,000
Other Assets Especially Mentioned | Commercial
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment					40,400,000
Other Assets Especially Mentioned | Owner occupied
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
2020	7.3		7.3
2019	8.7		8.7
2018	7.8		7.8
2017	3.1		3.1
2016	15.4		15.4
Prior	14.6		14.6
Revolving Loans Amortized Cost Basis	0.2		0.2
Total	57.1		57.1
Other Assets Especially Mentioned | Multi-family
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
2020	0		0
2019	0		0
2018	0		0
2017	0		0
2016	0		0
Prior	0		0
Revolving Loans Amortized Cost Basis	0		0
Total	0		0
Other Assets Especially Mentioned | Commercial and floor plans
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
2020	8.9		8.9
2019	1.2		1.2
2018	2.0		2.0
2017	7.3		7.3
2016	4.2		4.2
Prior	0.6		0.6
Revolving Loans Amortized Cost Basis	2.9		2.9
Total	27.1		27.1
Other Assets Especially Mentioned | Commercial purpose secured by 1-4 family
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
2020	0.3		0.3
2019	0.6		0.6
2018	0.3		0.3
2017	0.3		0.3
2016	0.6		0.6
Prior	0.9		0.9
Revolving Loans Amortized Cost Basis	0.4		0.4
Total	3.4		3.4
Other Assets Especially Mentioned | Agriculture Portfolio Segment [Member]
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
2020	2.6		2.6
2019	0.6		0.6
2018	0.5		0.5
2017	0.1		0.1
2016	0.1		0.1
Prior	0.4		0.4
Revolving Loans Amortized Cost Basis	13.8		13.8
Total	18.1		18.1
Loans held for investment					8,500,000
Substandard
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment					224,000,000.0
Substandard | Non-owner occupied
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
2020	15.9		15.9
2019	2.8		2.8
2018	0.9		0.9
2017	4.1		4.1
2016	1.1		1.1
Prior	14.8		14.8
Revolving Loans Amortized Cost Basis	0		0
Total	39.6		39.6
Substandard | Commercial Real Estate
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment					97,300,000
Substandard | Land acquisition & development
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
2020	0.4		0.4
2019	0		0
2018	1.2		1.2
2017	0.1		0.1
2016	0		0
Prior	0.2		0.2
Revolving Loans Amortized Cost Basis	0.4		0.4
Total	2.3		2.3
Loans held for investment					1,900,000
Substandard | Residential
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
2020	0.6		0.6
2019	0		0
2018	1.2		1.2
2017	0		0
2016	0		0
Prior	0		0
Revolving Loans Amortized Cost Basis	0		0
Total	1.8		1.8
Loans held for investment					2,200,000
Substandard | Commercial
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
2020	0		0
2019	0.8		0.8
2018	0		0
2017	0		0
2016	0		0
Prior	0.1		0.1
Revolving Loans Amortized Cost Basis	0		0
Total	0.9		0.9
Loans held for investment					1,500,000
Substandard | Total construction
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment					5,600,000
Substandard | Residential
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment					7,800,000
Substandard | Agricultural
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
2020	0.1		0.1
2019	8.3		8.3
2018	3.5		3.5
2017	1.1		1.1
2016	3.5		3.5
Prior	5.4		5.4
Revolving Loans Amortized Cost Basis	1.8		1.8
Total	23.7		23.7
Loans held for investment					26,600,000
Substandard | Real Estate Loan
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment					137,300,000
Substandard | Indirect consumer
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment					2,900,000
Substandard | Direct consumer
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment					800,000
Substandard | Credit card
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment					0
Substandard | Total consumer loans
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment					3,700,000
Substandard | Commercial
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment					60,300,000
Substandard | Owner occupied
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
2020	6.7		6.7
2019	6.6		6.6
2018	12.4		12.4
2017	5.2		5.2
2016	18.5		18.5
Prior	13.6		13.6
Revolving Loans Amortized Cost Basis	0.5		0.5
Total	63.5		63.5
Substandard | Multi-family
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
2020	0		0
2019	0		0
2018	0		0
2017	0		0
2016	0		0
Prior	0.1		0.1
Revolving Loans Amortized Cost Basis	0		0
Total	0.1		0.1
Substandard | Commercial and floor plans
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
2020	6.0		6.0
2019	4.6		4.6
2018	4.5		4.5
2017	0.5		0.5
2016	4.5		4.5
Prior	2.5		2.5
Revolving Loans Amortized Cost Basis	11.9		11.9
Total	34.5		34.5
Substandard | Commercial purpose secured by 1-4 family
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
2020	2.4		2.4
2019	1.1		1.1
2018	4.4		4.4
2017	0.3		0.3
2016	1.4		1.4
Prior	1.4		1.4
Revolving Loans Amortized Cost Basis	0.1		0.1
Total	11.1		11.1
Substandard | Agriculture Portfolio Segment [Member]
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
2020	6.4		6.4
2019	1.9		1.9
2018	4.3		4.3
2017	1.4		1.4
2016	0.1		0.1
Prior	0.4		0.4
Revolving Loans Amortized Cost Basis	8.2		8.2
Total	22.7		22.7
Loans held for investment					22,700,000
Doubtful
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment					5,900,000
Doubtful | Non-owner occupied
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
2020	0		0
2019	0		0
2018	0.2		0.2
2017	0		0
2016	0		0
Prior	0		0
Revolving Loans Amortized Cost Basis	0		0
Total	0.2		0.2
Doubtful | Commercial Real Estate
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment					800,000
Doubtful | Land acquisition & development
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
2020	0		0
2019	0		0
2018	0		0
2017	0		0
2016	0		0
Prior	0.1		0.1
Revolving Loans Amortized Cost Basis	0		0
Total	0.1		0.1
Loans held for investment					1,000,000.0
Doubtful | Residential
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
2020	0		0
2019	0		0
2018	0		0
2017	0		0
2016	0		0
Prior	0		0
Revolving Loans Amortized Cost Basis	0		0
Total	0		0
Loans held for investment					0
Doubtful | Commercial
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
2020	0		0
2019	0		0
2018	0.4		0.4
2017	0		0
2016	0		0
Prior	0		0
Revolving Loans Amortized Cost Basis	0		0
Total	0.4		0.4
Loans held for investment					0
Doubtful | Total construction
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment					1,000,000.0
Doubtful | Residential
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment					300,000
Doubtful | Agricultural
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
2020	0		0
2019	2.0		2.0
2018	0		0
2017	0		0
2016	0		0
Prior	0		0
Revolving Loans Amortized Cost Basis	0		0
Total	2.0		2.0
Loans held for investment					0
Doubtful | Real Estate Loan
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment					2,100,000
Doubtful | Indirect consumer
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment					0
Doubtful | Direct consumer
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment					100,000
Doubtful | Credit card
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment					0
Doubtful | Total consumer loans
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment					100,000
Doubtful | Commercial
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment					3,600,000
Doubtful | Owner occupied
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
2020	0.2		0.2
2019	0		0
2018	0		0
2017	0.1		0.1
2016	0		0
Prior	0.1		0.1
Revolving Loans Amortized Cost Basis	0		0
Total	0.4		0.4
Doubtful | Multi-family
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
2020	0		0
2019	0		0
2018	0		0
2017	0		0
2016	0		0
Prior	0		0
Revolving Loans Amortized Cost Basis	0		0
Total	0		0
Doubtful | Commercial and floor plans
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
2020	2.2		2.2
2019	3.7		3.7
2018	0.1		0.1
2017	0		0
2016	0.1		0.1
Prior	2.6		2.6
Revolving Loans Amortized Cost Basis	0.1		0.1
Total	8.8		8.8
Doubtful | Commercial purpose secured by 1-4 family
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
2020	0		0
2019	0		0
2018	0.1		0.1
2017	0		0
2016	0		0
Prior	0		0
Revolving Loans Amortized Cost Basis	0		0
Total	0.1		0.1
Doubtful | Agriculture Portfolio Segment [Member]
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
2020	0		0
2019	0.1		0.1
2018	0		0
2017	0.1		0.1
2016	0		0
Prior	0		0
Revolving Loans Amortized Cost Basis	0		0
Total	0.2		0.2
Loans held for investment					100,000
Total Criticized Loans
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment					387,400,000
Total Criticized Loans | Commercial Real Estate
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment					182,800,000
Total Criticized Loans | Land acquisition & development
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment					6,700,000
Total Criticized Loans | Residential
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment					3,100,000
Total Criticized Loans | Commercial
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment					3,200,000
Total Criticized Loans | Total construction
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment					13,000,000.0
Total Criticized Loans | Residential
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment					10,700,000
Total Criticized Loans | Agricultural
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment					40,900,000
Total Criticized Loans | Real Estate Loan
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment					247,400,000
Total Criticized Loans | Indirect consumer
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment					3,100,000
Total Criticized Loans | Direct consumer
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment					1,300,000
Total Criticized Loans | Credit card
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment					0
Total Criticized Loans | Total consumer loans
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment					4,400,000
Total Criticized Loans | Commercial
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment					104,300,000
Total Criticized Loans | Agriculture Portfolio Segment [Member]
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment					$ 31,300,000
Performing | Indirect consumer
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
2020	273.8		273.8
2019	212.9		212.9
2018	134.0		134.0
2017	85.9		85.9
2016	56.8		56.8
Prior	48.9		48.9
Revolving Loans Amortized Cost Basis	0		0
Total	812.3		812.3
Performing | Direct consumer
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
2020	40.6		40.6
2019	34.1		34.1
2018	33.9		33.9
2017	14.1		14.1
2016	6.5		6.5
Prior	9.8		9.8
Revolving Loans Amortized Cost Basis	22.9		22.9
Total	161.9		161.9
Performing | Credit card
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
2020	139.3		139.3
Performing | Residential 1-4 family
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
2020	311.1		311.1
2019	119.8		119.8
2018	71.4		71.4
2017	57.9		57.9
2016	76.9		76.9
Prior	270.2		270.2
Revolving Loans Amortized Cost Basis	0		0
Total	907.3		907.3
Performing | Consumer Home Equity and HELOC
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
2020	10.2		10.2
2019	8.3		8.3
2018	9.6		9.6
2017	10.7		10.7
2016	5.3		5.3
Prior	16.7		16.7
Revolving Loans Amortized Cost Basis	340.7		340.7
Total	401.5		401.5
Nonperforming | Indirect consumer
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
2020	0		0
2019	0.2		0.2
2018	0.1		0.1
2017	0		0
2016	0.1		0.1
Prior	0.1		0.1
Revolving Loans Amortized Cost Basis	0		0
Total	0.5		0.5
Nonperforming | Direct consumer
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
2020	0		0
2019	0		0
2018	0.1		0.1
2017	0.1		0.1
2016	0		0
Prior	0		0
Revolving Loans Amortized Cost Basis	0		0
Total	0.2		0.2
Nonperforming | Credit card
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
2020	1.0		1.0
Nonperforming | Residential 1-4 family
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
2020	0		0
2019	0.7		0.7
2018	0.2		0.2
2017	0		0
2016	0		0
Prior	0.9		0.9
Revolving Loans Amortized Cost Basis	0		0
Total	1.8		1.8
Nonperforming | Consumer Home Equity and HELOC
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
2020	0.1		0.1
2019	0		0
2018	0		0
2017	0.1		0.1
2016	0		0
Prior	0.4		0.4
Revolving Loans Amortized Cost Basis	0		0
Total	0.6		0.6
Agriculture Portfolio Segment [Member] | Credit card
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
2020	1.6		1.6
Agriculture Portfolio Segment [Member] | Performing | Credit card
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
2020	1.5		1.5
Agriculture Portfolio Segment [Member] | Nonperforming | Credit card
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
2020	0.1		0.1
Commercial | Credit card
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
2020	68.8		68.8
Commercial | Performing | Credit card
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
2020	68.5		68.5
Commercial | Nonperforming | Credit card
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
2020	0.3		0.3
Total consumer loans | Credit card
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
2020	69.9		69.9
Total consumer loans | Performing | Credit card
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
2020	69.3		69.3
Total consumer loans | Nonperforming | Credit card
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
2020	$ 0.6		$ 0.6