Loans Held for Investment - Schedule of Contractual Aging of Loans by Portfolio (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022	Dec. 31, 2022
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Nonaccrual loans	$ 31,600,000		$ 31,600,000		$ 39,800,000
Financing Receivable, Nonaccrual, Interest Income			0
Impaired Financing Receivable, Interest Income, Accrual Method	0	$ 0	0	$ 0
Less loans charged-off	6,200,000	16,200,000	29,200,000	39,800,000
Accrued interest reversal	(1,000,000)	0	1,900,000
Commercial real estate
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Loan in Process	1,600,000		1,600,000		7,500,000
Nonaccrual loans	31,000,000.0		31,000,000.0		19,600,000
Less loans charged-off		5,800,000	6,300,000	10,900,000
Financing Receivable, Excluding Accrued Interest, Revolving, Converted to Term Loan	21,600,000		21,600,000
Financing Receivable, Excluding Accrued Interest, Year One, Originated, Current Fiscal Year	876,700,000		876,700,000
Financing Receivable, Excluding Accrued Interest, Year Two, Originated, Fiscal Year before Current Fiscal Year	2,271,500,000		2,271,500,000
Financing Receivable, Excluding Accrued Interest, Year Three, Originated, Two Years before Current Fiscal Year	1,712,200,000		1,712,200,000
Financing Receivable, Excluding Accrued Interest, Year Four, Originated, Three Years before Current Fiscal Year	1,260,000,000		1,260,000,000
Financing Receivable, Excluding Accrued Interest, Year Five, Originated, Four Years before Current Fiscal Year	790,000,000.0		790,000,000.0
Financing Receivable, Excluding Accrued Interest, Originated, More than Five Years before Current Fiscal Year	1,790,400,000		1,790,400,000
Financing Receivable, Excluding Accrued Interest, Revolving	43,800,000		43,800,000
Total	8,766,200,000		8,766,200,000
Commercial real estate | Pass
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Excluding Accrued Interest, Revolving, Converted to Term Loan	21,600,000		21,600,000
Financing Receivable, Excluding Accrued Interest, Year One, Originated, Current Fiscal Year	845,800,000		845,800,000
Financing Receivable, Excluding Accrued Interest, Year Two, Originated, Fiscal Year before Current Fiscal Year	2,240,200,000		2,240,200,000
Financing Receivable, Excluding Accrued Interest, Year Three, Originated, Two Years before Current Fiscal Year	1,649,900,000		1,649,900,000
Financing Receivable, Excluding Accrued Interest, Year Four, Originated, Three Years before Current Fiscal Year	1,245,700,000		1,245,700,000
Financing Receivable, Excluding Accrued Interest, Year Five, Originated, Four Years before Current Fiscal Year	732,700,000		732,700,000
Financing Receivable, Excluding Accrued Interest, Originated, More than Five Years before Current Fiscal Year	1,741,500,000		1,741,500,000
Financing Receivable, Excluding Accrued Interest, Revolving	42,800,000		42,800,000
Total	8,520,200,000		8,520,200,000
Commercial real estate | Other Assets Especially Mentioned
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Excluding Accrued Interest, Revolving, Converted to Term Loan	0		0
Financing Receivable, Excluding Accrued Interest, Year One, Originated, Current Fiscal Year	2,900,000		2,900,000
Financing Receivable, Excluding Accrued Interest, Year Two, Originated, Fiscal Year before Current Fiscal Year	5,000,000.0		5,000,000.0
Financing Receivable, Excluding Accrued Interest, Year Three, Originated, Two Years before Current Fiscal Year	41,300,000		41,300,000
Financing Receivable, Excluding Accrued Interest, Year Four, Originated, Three Years before Current Fiscal Year	4,700,000		4,700,000
Financing Receivable, Excluding Accrued Interest, Year Five, Originated, Four Years before Current Fiscal Year	26,900,000		26,900,000
Financing Receivable, Excluding Accrued Interest, Originated, More than Five Years before Current Fiscal Year	20,500,000		20,500,000
Financing Receivable, Excluding Accrued Interest, Revolving	0		0
Total	101,300,000		101,300,000
Commercial real estate | Substandard
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Excluding Accrued Interest, Revolving, Converted to Term Loan	0		0
Financing Receivable, Excluding Accrued Interest, Year One, Originated, Current Fiscal Year	28,000,000.0		28,000,000.0
Financing Receivable, Excluding Accrued Interest, Year Two, Originated, Fiscal Year before Current Fiscal Year	26,000,000.0		26,000,000.0
Financing Receivable, Excluding Accrued Interest, Year Three, Originated, Two Years before Current Fiscal Year	19,600,000		19,600,000
Financing Receivable, Excluding Accrued Interest, Year Four, Originated, Three Years before Current Fiscal Year	9,600,000		9,600,000
Financing Receivable, Excluding Accrued Interest, Year Five, Originated, Four Years before Current Fiscal Year	30,400,000		30,400,000
Financing Receivable, Excluding Accrued Interest, Originated, More than Five Years before Current Fiscal Year	28,400,000		28,400,000
Financing Receivable, Excluding Accrued Interest, Revolving	1,000,000.0		1,000,000.0
Total	143,000,000.0		143,000,000.0
Commercial real estate | Doubtful
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Excluding Accrued Interest, Revolving, Converted to Term Loan	0		0
Financing Receivable, Excluding Accrued Interest, Year One, Originated, Current Fiscal Year	0		0
Financing Receivable, Excluding Accrued Interest, Year Two, Originated, Fiscal Year before Current Fiscal Year	300,000		300,000
Financing Receivable, Excluding Accrued Interest, Year Three, Originated, Two Years before Current Fiscal Year	1,400,000		1,400,000
Financing Receivable, Excluding Accrued Interest, Year Four, Originated, Three Years before Current Fiscal Year	0		0
Financing Receivable, Excluding Accrued Interest, Year Five, Originated, Four Years before Current Fiscal Year	0		0
Financing Receivable, Excluding Accrued Interest, Originated, More than Five Years before Current Fiscal Year	0		0
Financing Receivable, Excluding Accrued Interest, Revolving	0		0
Total	1,700,000		1,700,000
Residential construction
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Less loans charged-off		0		0
Financing Receivable, Excluding Accrued Interest, Year One, Originated, Current Fiscal Year					118,400,000
Financing Receivable, Excluding Accrued Interest, Year Two, Originated, Fiscal Year before Current Fiscal Year					120,400,000
Financing Receivable, Excluding Accrued Interest, Year Three, Originated, Two Years before Current Fiscal Year					400,000
Financing Receivable, Excluding Accrued Interest, Year Four, Originated, Three Years before Current Fiscal Year					300,000
Financing Receivable, Excluding Accrued Interest, Year Five, Originated, Four Years before Current Fiscal Year					400,000
Financing Receivable, Excluding Accrued Interest, Originated, More than Five Years before Current Fiscal Year					6,200,000
Financing Receivable, Excluding Accrued Interest, Revolving					270,100,000
Total					516,200,000
Residential construction | Pass
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Excluding Accrued Interest, Year One, Originated, Current Fiscal Year					118,400,000
Financing Receivable, Excluding Accrued Interest, Year Two, Originated, Fiscal Year before Current Fiscal Year					119,900,000
Financing Receivable, Excluding Accrued Interest, Year Three, Originated, Two Years before Current Fiscal Year					400,000
Financing Receivable, Excluding Accrued Interest, Year Four, Originated, Three Years before Current Fiscal Year					300,000
Financing Receivable, Excluding Accrued Interest, Year Five, Originated, Four Years before Current Fiscal Year					400,000
Financing Receivable, Excluding Accrued Interest, Originated, More than Five Years before Current Fiscal Year					5,800,000
Financing Receivable, Excluding Accrued Interest, Revolving					270,100,000
Total					515,300,000
Residential construction | Substandard
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Excluding Accrued Interest, Year One, Originated, Current Fiscal Year					0
Financing Receivable, Excluding Accrued Interest, Year Two, Originated, Fiscal Year before Current Fiscal Year					500,000
Financing Receivable, Excluding Accrued Interest, Year Three, Originated, Two Years before Current Fiscal Year					0
Financing Receivable, Excluding Accrued Interest, Year Four, Originated, Three Years before Current Fiscal Year					0
Financing Receivable, Excluding Accrued Interest, Year Five, Originated, Four Years before Current Fiscal Year					0
Financing Receivable, Excluding Accrued Interest, Originated, More than Five Years before Current Fiscal Year					400,000
Financing Receivable, Excluding Accrued Interest, Revolving					0
Total					900,000
Commercial construction
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Less loans charged-off		6,600,000		6,600,000
Financing Receivable, Excluding Accrued Interest, Year One, Originated, Current Fiscal Year					461,800,000
Financing Receivable, Excluding Accrued Interest, Year Two, Originated, Fiscal Year before Current Fiscal Year					399,200,000
Financing Receivable, Excluding Accrued Interest, Year Three, Originated, Two Years before Current Fiscal Year					112,800,000
Financing Receivable, Excluding Accrued Interest, Year Four, Originated, Three Years before Current Fiscal Year					45,900,000
Financing Receivable, Excluding Accrued Interest, Year Five, Originated, Four Years before Current Fiscal Year					400,000
Financing Receivable, Excluding Accrued Interest, Originated, More than Five Years before Current Fiscal Year					0
Financing Receivable, Excluding Accrued Interest, Revolving					21,900,000
Total					1,042,000,000
Commercial construction | Pass
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Excluding Accrued Interest, Year One, Originated, Current Fiscal Year					442,700,000
Financing Receivable, Excluding Accrued Interest, Year Two, Originated, Fiscal Year before Current Fiscal Year					374,800,000
Financing Receivable, Excluding Accrued Interest, Year Three, Originated, Two Years before Current Fiscal Year					89,700,000
Financing Receivable, Excluding Accrued Interest, Year Four, Originated, Three Years before Current Fiscal Year					45,900,000
Financing Receivable, Excluding Accrued Interest, Year Five, Originated, Four Years before Current Fiscal Year					400,000
Financing Receivable, Excluding Accrued Interest, Originated, More than Five Years before Current Fiscal Year					0
Financing Receivable, Excluding Accrued Interest, Revolving					10,600,000
Total					964,100,000
Commercial construction | Other Assets Especially Mentioned
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Excluding Accrued Interest, Year One, Originated, Current Fiscal Year					2,300,000
Financing Receivable, Excluding Accrued Interest, Year Two, Originated, Fiscal Year before Current Fiscal Year					0
Financing Receivable, Excluding Accrued Interest, Year Three, Originated, Two Years before Current Fiscal Year					23,100,000
Financing Receivable, Excluding Accrued Interest, Year Four, Originated, Three Years before Current Fiscal Year					0
Financing Receivable, Excluding Accrued Interest, Year Five, Originated, Four Years before Current Fiscal Year					0
Financing Receivable, Excluding Accrued Interest, Originated, More than Five Years before Current Fiscal Year					0
Financing Receivable, Excluding Accrued Interest, Revolving					11,300,000
Total					36,700,000
Commercial construction | Substandard
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Excluding Accrued Interest, Year One, Originated, Current Fiscal Year					16,800,000
Financing Receivable, Excluding Accrued Interest, Year Two, Originated, Fiscal Year before Current Fiscal Year					24,400,000
Financing Receivable, Excluding Accrued Interest, Year Three, Originated, Two Years before Current Fiscal Year					0
Financing Receivable, Excluding Accrued Interest, Year Four, Originated, Three Years before Current Fiscal Year					0
Financing Receivable, Excluding Accrued Interest, Year Five, Originated, Four Years before Current Fiscal Year					0
Financing Receivable, Excluding Accrued Interest, Originated, More than Five Years before Current Fiscal Year					0
Financing Receivable, Excluding Accrued Interest, Revolving					0
Total					41,200,000
Total construction loans
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Loan in Process	14,500,000		14,500,000		11,600,000
Nonaccrual loans	17,400,000		17,400,000		3,700,000
Less loans charged-off			9,700,000
Financing Receivable, Excluding Accrued Interest, Revolving, Converted to Term Loan	3,400,000		3,400,000
Financing Receivable, Excluding Accrued Interest, Year One, Originated, Current Fiscal Year	450,400,000		450,400,000
Financing Receivable, Excluding Accrued Interest, Year Two, Originated, Fiscal Year before Current Fiscal Year	833,900,000		833,900,000
Financing Receivable, Excluding Accrued Interest, Year Three, Originated, Two Years before Current Fiscal Year	444,300,000		444,300,000
Financing Receivable, Excluding Accrued Interest, Year Four, Originated, Three Years before Current Fiscal Year	39,600,000		39,600,000
Financing Receivable, Excluding Accrued Interest, Year Five, Originated, Four Years before Current Fiscal Year	16,500,000		16,500,000
Financing Receivable, Excluding Accrued Interest, Originated, More than Five Years before Current Fiscal Year	39,400,000		39,400,000
Financing Receivable, Excluding Accrued Interest, Revolving	102,800,000		102,800,000
Total	1,930,300,000		1,930,300,000
Total construction loans | Pass
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Excluding Accrued Interest, Revolving, Converted to Term Loan	2,600,000		2,600,000
Financing Receivable, Excluding Accrued Interest, Year One, Originated, Current Fiscal Year	444,900,000		444,900,000
Financing Receivable, Excluding Accrued Interest, Year Two, Originated, Fiscal Year before Current Fiscal Year	806,100,000		806,100,000
Financing Receivable, Excluding Accrued Interest, Year Three, Originated, Two Years before Current Fiscal Year	413,300,000		413,300,000
Financing Receivable, Excluding Accrued Interest, Year Four, Originated, Three Years before Current Fiscal Year	39,400,000		39,400,000
Financing Receivable, Excluding Accrued Interest, Year Five, Originated, Four Years before Current Fiscal Year	16,500,000		16,500,000
Financing Receivable, Excluding Accrued Interest, Originated, More than Five Years before Current Fiscal Year	38,700,000		38,700,000
Financing Receivable, Excluding Accrued Interest, Revolving	102,800,000		102,800,000
Total	1,864,300,000		1,864,300,000
Total construction loans | Other Assets Especially Mentioned
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Excluding Accrued Interest, Revolving, Converted to Term Loan	800,000		800,000
Financing Receivable, Excluding Accrued Interest, Year One, Originated, Current Fiscal Year	4,100,000		4,100,000
Financing Receivable, Excluding Accrued Interest, Year Two, Originated, Fiscal Year before Current Fiscal Year	11,400,000		11,400,000
Financing Receivable, Excluding Accrued Interest, Year Three, Originated, Two Years before Current Fiscal Year	6,500,000		6,500,000
Financing Receivable, Excluding Accrued Interest, Year Four, Originated, Three Years before Current Fiscal Year	0		0
Financing Receivable, Excluding Accrued Interest, Year Five, Originated, Four Years before Current Fiscal Year	0		0
Financing Receivable, Excluding Accrued Interest, Originated, More than Five Years before Current Fiscal Year	200,000		200,000
Financing Receivable, Excluding Accrued Interest, Revolving	0		0
Total	23,000,000.0		23,000,000.0
Total construction loans | Substandard
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Excluding Accrued Interest, Revolving, Converted to Term Loan	0		0
Financing Receivable, Excluding Accrued Interest, Year One, Originated, Current Fiscal Year	1,400,000		1,400,000
Financing Receivable, Excluding Accrued Interest, Year Two, Originated, Fiscal Year before Current Fiscal Year	3,300,000		3,300,000
Financing Receivable, Excluding Accrued Interest, Year Three, Originated, Two Years before Current Fiscal Year	24,500,000		24,500,000
Financing Receivable, Excluding Accrued Interest, Year Four, Originated, Three Years before Current Fiscal Year	200,000		200,000
Financing Receivable, Excluding Accrued Interest, Year Five, Originated, Four Years before Current Fiscal Year	0		0
Financing Receivable, Excluding Accrued Interest, Originated, More than Five Years before Current Fiscal Year	500,000		500,000
Financing Receivable, Excluding Accrued Interest, Revolving	0		0
Total	29,900,000		29,900,000
Total construction loans | Doubtful
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Excluding Accrued Interest, Revolving, Converted to Term Loan	0		0
Financing Receivable, Excluding Accrued Interest, Year One, Originated, Current Fiscal Year	0		0
Financing Receivable, Excluding Accrued Interest, Year Two, Originated, Fiscal Year before Current Fiscal Year	13,100,000		13,100,000
Financing Receivable, Excluding Accrued Interest, Year Three, Originated, Two Years before Current Fiscal Year	0		0
Financing Receivable, Excluding Accrued Interest, Year Four, Originated, Three Years before Current Fiscal Year	0		0
Financing Receivable, Excluding Accrued Interest, Year Five, Originated, Four Years before Current Fiscal Year	0		0
Financing Receivable, Excluding Accrued Interest, Originated, More than Five Years before Current Fiscal Year	0		0
Financing Receivable, Excluding Accrued Interest, Revolving	0		0
Total	13,100,000		13,100,000
Residential
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Loan in Process	5,200,000		5,200,000		13,200,000
Nonaccrual loans	9,500,000		9,500,000		6,400,000
Less loans charged-off		100,000	600,000	200,000
Financing Receivable, Excluding Accrued Interest, Revolving, Converted to Term Loan	24,500,000		24,500,000
Financing Receivable, Excluding Accrued Interest, Year One, Originated, Current Fiscal Year	39,300,000		39,300,000
Financing Receivable, Excluding Accrued Interest, Year Two, Originated, Fiscal Year before Current Fiscal Year	319,100,000		319,100,000
Financing Receivable, Excluding Accrued Interest, Year Three, Originated, Two Years before Current Fiscal Year	514,200,000		514,200,000
Financing Receivable, Excluding Accrued Interest, Year Four, Originated, Three Years before Current Fiscal Year	513,400,000		513,400,000
Financing Receivable, Excluding Accrued Interest, Year Five, Originated, Four Years before Current Fiscal Year	93,100,000		93,100,000
Financing Receivable, Excluding Accrued Interest, Originated, More than Five Years before Current Fiscal Year	233,000,000.0		233,000,000.0
Financing Receivable, Excluding Accrued Interest, Revolving	475,600,000		475,600,000
Total	2,212,200,000		2,212,200,000
Residential | Performing
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Excluding Accrued Interest, Revolving, Converted to Term Loan	24,500,000		24,500,000
Financing Receivable, Excluding Accrued Interest, Year One, Originated, Current Fiscal Year	38,600,000		38,600,000
Financing Receivable, Excluding Accrued Interest, Year Two, Originated, Fiscal Year before Current Fiscal Year	317,500,000		317,500,000
Financing Receivable, Excluding Accrued Interest, Year Three, Originated, Two Years before Current Fiscal Year	513,200,000		513,200,000
Financing Receivable, Excluding Accrued Interest, Year Four, Originated, Three Years before Current Fiscal Year	512,800,000		512,800,000
Financing Receivable, Excluding Accrued Interest, Year Five, Originated, Four Years before Current Fiscal Year	92,300,000		92,300,000
Financing Receivable, Excluding Accrued Interest, Originated, More than Five Years before Current Fiscal Year	227,200,000		227,200,000
Financing Receivable, Excluding Accrued Interest, Revolving	475,600,000		475,600,000
Total	2,201,700,000		2,201,700,000
Residential | Nonperforming
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Excluding Accrued Interest, Revolving, Converted to Term Loan	0		0
Financing Receivable, Excluding Accrued Interest, Year One, Originated, Current Fiscal Year	700,000		700,000
Financing Receivable, Excluding Accrued Interest, Year Two, Originated, Fiscal Year before Current Fiscal Year	1,600,000		1,600,000
Financing Receivable, Excluding Accrued Interest, Year Three, Originated, Two Years before Current Fiscal Year	1,000,000.0		1,000,000.0
Financing Receivable, Excluding Accrued Interest, Year Four, Originated, Three Years before Current Fiscal Year	600,000		600,000
Financing Receivable, Excluding Accrued Interest, Year Five, Originated, Four Years before Current Fiscal Year	800,000		800,000
Financing Receivable, Excluding Accrued Interest, Originated, More than Five Years before Current Fiscal Year	5,800,000		5,800,000
Financing Receivable, Excluding Accrued Interest, Revolving	0		0
Total	10,500,000		10,500,000
Agricultural
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Loan in Process	1,900,000		1,900,000		7,200,000
Nonaccrual loans	5,400,000		5,400,000		7,600,000
Less loans charged-off		0	0	200,000
Financing Receivable, Excluding Accrued Interest, Revolving, Converted to Term Loan	100,000		100,000
Financing Receivable, Excluding Accrued Interest, Year One, Originated, Current Fiscal Year	72,100,000		72,100,000		204,200,000
Financing Receivable, Excluding Accrued Interest, Year Two, Originated, Fiscal Year before Current Fiscal Year	159,500,000		159,500,000		185,800,000
Financing Receivable, Excluding Accrued Interest, Year Three, Originated, Two Years before Current Fiscal Year	165,000,000.0		165,000,000.0		115,500,000
Financing Receivable, Excluding Accrued Interest, Year Four, Originated, Three Years before Current Fiscal Year	100,200,000		100,200,000		68,000,000.0
Financing Receivable, Excluding Accrued Interest, Year Five, Originated, Four Years before Current Fiscal Year	61,700,000		61,700,000		59,300,000
Financing Receivable, Excluding Accrued Interest, Originated, More than Five Years before Current Fiscal Year	144,600,000		144,600,000		119,600,000
Financing Receivable, Excluding Accrued Interest, Revolving	28,300,000		28,300,000		42,500,000
Total	731,500,000		731,500,000		794,900,000
Agricultural | Pass
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Excluding Accrued Interest, Revolving, Converted to Term Loan	100,000		100,000
Financing Receivable, Excluding Accrued Interest, Year One, Originated, Current Fiscal Year	60,500,000		60,500,000		180,000,000.0
Financing Receivable, Excluding Accrued Interest, Year Two, Originated, Fiscal Year before Current Fiscal Year	133,100,000		133,100,000		172,800,000
Financing Receivable, Excluding Accrued Interest, Year Three, Originated, Two Years before Current Fiscal Year	158,800,000		158,800,000		109,500,000
Financing Receivable, Excluding Accrued Interest, Year Four, Originated, Three Years before Current Fiscal Year	95,900,000		95,900,000		64,800,000
Financing Receivable, Excluding Accrued Interest, Year Five, Originated, Four Years before Current Fiscal Year	59,400,000		59,400,000		46,600,000
Financing Receivable, Excluding Accrued Interest, Originated, More than Five Years before Current Fiscal Year	130,100,000		130,100,000		105,100,000
Financing Receivable, Excluding Accrued Interest, Revolving	27,800,000		27,800,000		31,400,000
Total	665,700,000		665,700,000		710,200,000
Agricultural | Other Assets Especially Mentioned
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Excluding Accrued Interest, Revolving, Converted to Term Loan	0		0
Financing Receivable, Excluding Accrued Interest, Year One, Originated, Current Fiscal Year	3,500,000		3,500,000		22,400,000
Financing Receivable, Excluding Accrued Interest, Year Two, Originated, Fiscal Year before Current Fiscal Year	6,600,000		6,600,000		700,000
Financing Receivable, Excluding Accrued Interest, Year Three, Originated, Two Years before Current Fiscal Year	1,400,000		1,400,000		1,200,000
Financing Receivable, Excluding Accrued Interest, Year Four, Originated, Three Years before Current Fiscal Year	2,100,000		2,100,000		2,600,000
Financing Receivable, Excluding Accrued Interest, Year Five, Originated, Four Years before Current Fiscal Year	1,800,000		1,800,000		10,000,000.0
Financing Receivable, Excluding Accrued Interest, Originated, More than Five Years before Current Fiscal Year	5,900,000		5,900,000		3,200,000
Financing Receivable, Excluding Accrued Interest, Revolving	500,000		500,000		11,000,000.0
Total	21,800,000		21,800,000		51,100,000
Agricultural | Substandard
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Excluding Accrued Interest, Revolving, Converted to Term Loan	0		0
Financing Receivable, Excluding Accrued Interest, Year One, Originated, Current Fiscal Year	8,100,000		8,100,000		1,800,000
Financing Receivable, Excluding Accrued Interest, Year Two, Originated, Fiscal Year before Current Fiscal Year	19,800,000		19,800,000		12,300,000
Financing Receivable, Excluding Accrued Interest, Year Three, Originated, Two Years before Current Fiscal Year	4,800,000		4,800,000		3,500,000
Financing Receivable, Excluding Accrued Interest, Year Four, Originated, Three Years before Current Fiscal Year	2,200,000		2,200,000		600,000
Financing Receivable, Excluding Accrued Interest, Year Five, Originated, Four Years before Current Fiscal Year	500,000		500,000		2,700,000
Financing Receivable, Excluding Accrued Interest, Originated, More than Five Years before Current Fiscal Year	8,600,000		8,600,000		11,300,000
Financing Receivable, Excluding Accrued Interest, Revolving	0		0		100,000
Total	44,000,000.0		44,000,000.0		32,300,000
Agricultural | Doubtful
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Excluding Accrued Interest, Year One, Originated, Current Fiscal Year					0
Financing Receivable, Excluding Accrued Interest, Year Two, Originated, Fiscal Year before Current Fiscal Year					0
Financing Receivable, Excluding Accrued Interest, Year Three, Originated, Two Years before Current Fiscal Year					1,300,000
Financing Receivable, Excluding Accrued Interest, Year Four, Originated, Three Years before Current Fiscal Year					0
Financing Receivable, Excluding Accrued Interest, Year Five, Originated, Four Years before Current Fiscal Year					0
Financing Receivable, Excluding Accrued Interest, Originated, More than Five Years before Current Fiscal Year					0
Financing Receivable, Excluding Accrued Interest, Revolving					0
Total					1,300,000
Total real estate
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Loan in Process	23,200,000		23,200,000		39,500,000
Nonaccrual loans	63,300,000		63,300,000		37,300,000
Less loans charged-off	1,800,000	12,500,000	16,600,000	20,600,000
Indirect consumer
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Loan in Process	9,000,000.0		9,000,000.0		12,300,000
Nonaccrual loans	3,000,000.0		3,000,000.0		2,700,000
Less loans charged-off		1,200,000	5,200,000	2,900,000
Financing Receivable, Excluding Accrued Interest, Revolving, Converted to Term Loan	0		0
Financing Receivable, Excluding Accrued Interest, Year One, Originated, Current Fiscal Year	142,900,000		142,900,000		381,300,000
Financing Receivable, Excluding Accrued Interest, Year Two, Originated, Fiscal Year before Current Fiscal Year	293,600,000		293,600,000		177,300,000
Financing Receivable, Excluding Accrued Interest, Year Three, Originated, Two Years before Current Fiscal Year	129,000,000.0		129,000,000.0		130,600,000
Financing Receivable, Excluding Accrued Interest, Year Four, Originated, Three Years before Current Fiscal Year	92,700,000		92,700,000		60,000,000.0
Financing Receivable, Excluding Accrued Interest, Year Five, Originated, Four Years before Current Fiscal Year	38,700,000		38,700,000		33,800,000
Financing Receivable, Excluding Accrued Interest, Originated, More than Five Years before Current Fiscal Year	54,800,000		54,800,000		46,700,000
Financing Receivable, Excluding Accrued Interest, Revolving	0		0		0
Total	751,700,000		751,700,000		829,700,000
Indirect consumer | Performing
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Excluding Accrued Interest, Revolving, Converted to Term Loan	0		0
Financing Receivable, Excluding Accrued Interest, Year One, Originated, Current Fiscal Year	142,500,000		142,500,000		380,300,000
Financing Receivable, Excluding Accrued Interest, Year Two, Originated, Fiscal Year before Current Fiscal Year	292,400,000		292,400,000		176,400,000
Financing Receivable, Excluding Accrued Interest, Year Three, Originated, Two Years before Current Fiscal Year	128,300,000		128,300,000		130,000,000.0
Financing Receivable, Excluding Accrued Interest, Year Four, Originated, Three Years before Current Fiscal Year	92,300,000		92,300,000		59,700,000
Financing Receivable, Excluding Accrued Interest, Year Five, Originated, Four Years before Current Fiscal Year	38,500,000		38,500,000		33,600,000
Financing Receivable, Excluding Accrued Interest, Originated, More than Five Years before Current Fiscal Year	54,300,000		54,300,000		46,300,000
Financing Receivable, Excluding Accrued Interest, Revolving	0		0		0
Total	748,300,000		748,300,000		826,300,000
Indirect consumer | Nonperforming
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Excluding Accrued Interest, Revolving, Converted to Term Loan	0		0
Financing Receivable, Excluding Accrued Interest, Year One, Originated, Current Fiscal Year	400,000		400,000		1,000,000.0
Financing Receivable, Excluding Accrued Interest, Year Two, Originated, Fiscal Year before Current Fiscal Year	1,200,000		1,200,000		900,000
Financing Receivable, Excluding Accrued Interest, Year Three, Originated, Two Years before Current Fiscal Year	700,000		700,000		600,000
Financing Receivable, Excluding Accrued Interest, Year Four, Originated, Three Years before Current Fiscal Year	400,000		400,000		300,000
Financing Receivable, Excluding Accrued Interest, Year Five, Originated, Four Years before Current Fiscal Year	200,000		200,000		200,000
Financing Receivable, Excluding Accrued Interest, Originated, More than Five Years before Current Fiscal Year	500,000		500,000		400,000
Financing Receivable, Excluding Accrued Interest, Revolving	0		0		0
Total	3,400,000		3,400,000		3,400,000
Direct and advance lines
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Loan in Process	800,000		800,000		1,200,000
Nonaccrual loans	200,000		200,000		300,000
Less loans charged-off		1,400,000	3,200,000	2,800,000
Financing Receivable, Excluding Accrued Interest, Revolving, Converted to Term Loan	200,000		200,000
Financing Receivable, Excluding Accrued Interest, Year One, Originated, Current Fiscal Year	35,300,000		35,300,000		52,700,000
Financing Receivable, Excluding Accrued Interest, Year Two, Originated, Fiscal Year before Current Fiscal Year	36,900,000		36,900,000		32,000,000.0
Financing Receivable, Excluding Accrued Interest, Year Three, Originated, Two Years before Current Fiscal Year	21,200,000		21,200,000		18,300,000
Financing Receivable, Excluding Accrued Interest, Year Four, Originated, Three Years before Current Fiscal Year	10,800,000		10,800,000		8,500,000
Financing Receivable, Excluding Accrued Interest, Year Five, Originated, Four Years before Current Fiscal Year	4,400,000		4,400,000		6,500,000
Financing Receivable, Excluding Accrued Interest, Originated, More than Five Years before Current Fiscal Year	7,000,000.0		7,000,000.0		9,000,000.0
Financing Receivable, Excluding Accrued Interest, Revolving	26,500,000		26,500,000		25,900,000
Total	142,300,000		142,300,000		152,900,000
Direct and advance lines | Performing
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Excluding Accrued Interest, Revolving, Converted to Term Loan	200,000		200,000
Financing Receivable, Excluding Accrued Interest, Year One, Originated, Current Fiscal Year	35,300,000		35,300,000		52,600,000
Financing Receivable, Excluding Accrued Interest, Year Two, Originated, Fiscal Year before Current Fiscal Year	36,800,000		36,800,000		31,900,000
Financing Receivable, Excluding Accrued Interest, Year Three, Originated, Two Years before Current Fiscal Year	21,100,000		21,100,000		18,200,000
Financing Receivable, Excluding Accrued Interest, Year Four, Originated, Three Years before Current Fiscal Year	10,800,000		10,800,000		8,500,000
Financing Receivable, Excluding Accrued Interest, Year Five, Originated, Four Years before Current Fiscal Year	4,400,000		4,400,000		6,500,000
Financing Receivable, Excluding Accrued Interest, Originated, More than Five Years before Current Fiscal Year	7,000,000.0		7,000,000.0		8,900,000
Financing Receivable, Excluding Accrued Interest, Revolving	26,500,000		26,500,000		25,800,000
Total	142,100,000		142,100,000		152,400,000
Direct and advance lines | Nonperforming
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Excluding Accrued Interest, Revolving, Converted to Term Loan	0		0
Financing Receivable, Excluding Accrued Interest, Year One, Originated, Current Fiscal Year	0		0		100,000
Financing Receivable, Excluding Accrued Interest, Year Two, Originated, Fiscal Year before Current Fiscal Year	100,000		100,000		100,000
Financing Receivable, Excluding Accrued Interest, Year Three, Originated, Two Years before Current Fiscal Year	100,000		100,000		100,000
Financing Receivable, Excluding Accrued Interest, Year Four, Originated, Three Years before Current Fiscal Year	0		0		0
Financing Receivable, Excluding Accrued Interest, Year Five, Originated, Four Years before Current Fiscal Year	0		0		0
Financing Receivable, Excluding Accrued Interest, Originated, More than Five Years before Current Fiscal Year	0		0		100,000
Financing Receivable, Excluding Accrued Interest, Revolving	0		0		100,000
Total	200,000		200,000		500,000
Credit card
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Loan in Process	1,500,000		1,500,000		1,800,000
Nonaccrual loans	0		0		0
Less loans charged-off		300,000	2,000,000.0	1,800,000
Financing Receivable, Excluding Accrued Interest, Revolving, Converted to Term Loan	0		0
Financing Receivable, Excluding Accrued Interest, Year One, Originated, Current Fiscal Year	0		0		178,100,000
Financing Receivable, Excluding Accrued Interest, Year Two, Originated, Fiscal Year before Current Fiscal Year	0		0
Financing Receivable, Excluding Accrued Interest, Year Three, Originated, Two Years before Current Fiscal Year	0		0
Financing Receivable, Excluding Accrued Interest, Year Four, Originated, Three Years before Current Fiscal Year	0		0
Financing Receivable, Excluding Accrued Interest, Year Five, Originated, Four Years before Current Fiscal Year	0		0
Financing Receivable, Excluding Accrued Interest, Originated, More than Five Years before Current Fiscal Year	0		0
Financing Receivable, Excluding Accrued Interest, Revolving	71,600,000		71,600,000
Total	71,600,000		71,600,000
Credit card | Performing
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Excluding Accrued Interest, Revolving, Converted to Term Loan	0		0
Financing Receivable, Excluding Accrued Interest, Year One, Originated, Current Fiscal Year	0		0		177,300,000
Financing Receivable, Excluding Accrued Interest, Year Two, Originated, Fiscal Year before Current Fiscal Year	0		0
Financing Receivable, Excluding Accrued Interest, Year Three, Originated, Two Years before Current Fiscal Year	0		0
Financing Receivable, Excluding Accrued Interest, Year Four, Originated, Three Years before Current Fiscal Year	0		0
Financing Receivable, Excluding Accrued Interest, Year Five, Originated, Four Years before Current Fiscal Year	0		0
Financing Receivable, Excluding Accrued Interest, Originated, More than Five Years before Current Fiscal Year	0		0
Financing Receivable, Excluding Accrued Interest, Revolving	71,100,000		71,100,000
Total	71,100,000		71,100,000
Credit card | Nonperforming
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Excluding Accrued Interest, Revolving, Converted to Term Loan	0		0
Financing Receivable, Excluding Accrued Interest, Year One, Originated, Current Fiscal Year	0		0		800,000
Financing Receivable, Excluding Accrued Interest, Year Two, Originated, Fiscal Year before Current Fiscal Year	0		0
Financing Receivable, Excluding Accrued Interest, Year Three, Originated, Two Years before Current Fiscal Year	0		0
Financing Receivable, Excluding Accrued Interest, Year Four, Originated, Three Years before Current Fiscal Year	0		0
Financing Receivable, Excluding Accrued Interest, Year Five, Originated, Four Years before Current Fiscal Year	0		0
Financing Receivable, Excluding Accrued Interest, Originated, More than Five Years before Current Fiscal Year	0		0
Financing Receivable, Excluding Accrued Interest, Revolving	500,000		500,000
Total	500,000		500,000
Total consumer loans
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Loan in Process	11,300,000		11,300,000		15,300,000
Nonaccrual loans	3,200,000		3,200,000		3,000,000.0
Less loans charged-off	3,700,000	2,900,000	10,400,000	7,500,000
Commercial
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Loan in Process	18,900,000		18,900,000		10,900,000
Nonaccrual loans	12,000,000.0		12,000,000.0		10,200,000
Less loans charged-off	700,000	800,000	2,200,000	6,300,000
Financing Receivable, Excluding Accrued Interest, Revolving, Converted to Term Loan	10,000,000.0		10,000,000.0
Financing Receivable, Excluding Accrued Interest, Year One, Originated, Current Fiscal Year	395,800,000		395,800,000
Financing Receivable, Excluding Accrued Interest, Year Two, Originated, Fiscal Year before Current Fiscal Year	565,600,000		565,600,000
Financing Receivable, Excluding Accrued Interest, Year Three, Originated, Two Years before Current Fiscal Year	427,300,000		427,300,000
Financing Receivable, Excluding Accrued Interest, Year Four, Originated, Three Years before Current Fiscal Year	236,400,000		236,400,000
Financing Receivable, Excluding Accrued Interest, Year Five, Originated, Four Years before Current Fiscal Year	123,500,000		123,500,000
Financing Receivable, Excluding Accrued Interest, Originated, More than Five Years before Current Fiscal Year	323,400,000		323,400,000
Financing Receivable, Excluding Accrued Interest, Revolving	843,100,000		843,100,000
Total	2,925,100,000		2,925,100,000
Commercial | Pass
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Excluding Accrued Interest, Revolving, Converted to Term Loan	9,500,000		9,500,000
Financing Receivable, Excluding Accrued Interest, Year One, Originated, Current Fiscal Year	383,800,000		383,800,000
Financing Receivable, Excluding Accrued Interest, Year Two, Originated, Fiscal Year before Current Fiscal Year	537,200,000		537,200,000
Financing Receivable, Excluding Accrued Interest, Year Three, Originated, Two Years before Current Fiscal Year	408,500,000		408,500,000
Financing Receivable, Excluding Accrued Interest, Year Four, Originated, Three Years before Current Fiscal Year	224,500,000		224,500,000
Financing Receivable, Excluding Accrued Interest, Year Five, Originated, Four Years before Current Fiscal Year	116,400,000		116,400,000
Financing Receivable, Excluding Accrued Interest, Originated, More than Five Years before Current Fiscal Year	317,000,000.0		317,000,000.0
Financing Receivable, Excluding Accrued Interest, Revolving	765,800,000		765,800,000
Total	2,762,700,000		2,762,700,000
Commercial | Other Assets Especially Mentioned
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Excluding Accrued Interest, Revolving, Converted to Term Loan	100,000		100,000
Financing Receivable, Excluding Accrued Interest, Year One, Originated, Current Fiscal Year	2,300,000		2,300,000
Financing Receivable, Excluding Accrued Interest, Year Two, Originated, Fiscal Year before Current Fiscal Year	4,900,000		4,900,000
Financing Receivable, Excluding Accrued Interest, Year Three, Originated, Two Years before Current Fiscal Year	6,700,000		6,700,000
Financing Receivable, Excluding Accrued Interest, Year Four, Originated, Three Years before Current Fiscal Year	4,700,000		4,700,000
Financing Receivable, Excluding Accrued Interest, Year Five, Originated, Four Years before Current Fiscal Year	2,500,000		2,500,000
Financing Receivable, Excluding Accrued Interest, Originated, More than Five Years before Current Fiscal Year	1,400,000		1,400,000
Financing Receivable, Excluding Accrued Interest, Revolving	14,800,000		14,800,000
Total	37,400,000		37,400,000
Commercial | Substandard
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Excluding Accrued Interest, Revolving, Converted to Term Loan	400,000		400,000
Financing Receivable, Excluding Accrued Interest, Year One, Originated, Current Fiscal Year	5,000,000.0		5,000,000.0
Financing Receivable, Excluding Accrued Interest, Year Two, Originated, Fiscal Year before Current Fiscal Year	23,300,000		23,300,000
Financing Receivable, Excluding Accrued Interest, Year Three, Originated, Two Years before Current Fiscal Year	10,900,000		10,900,000
Financing Receivable, Excluding Accrued Interest, Year Four, Originated, Three Years before Current Fiscal Year	7,200,000		7,200,000
Financing Receivable, Excluding Accrued Interest, Year Five, Originated, Four Years before Current Fiscal Year	4,600,000		4,600,000
Financing Receivable, Excluding Accrued Interest, Originated, More than Five Years before Current Fiscal Year	5,000,000.0		5,000,000.0
Financing Receivable, Excluding Accrued Interest, Revolving	62,400,000		62,400,000
Total	118,800,000		118,800,000
Commercial | Doubtful
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Excluding Accrued Interest, Revolving, Converted to Term Loan	0		0
Financing Receivable, Excluding Accrued Interest, Year One, Originated, Current Fiscal Year	4,700,000		4,700,000
Financing Receivable, Excluding Accrued Interest, Year Two, Originated, Fiscal Year before Current Fiscal Year	200,000		200,000
Financing Receivable, Excluding Accrued Interest, Year Three, Originated, Two Years before Current Fiscal Year	1,200,000		1,200,000
Financing Receivable, Excluding Accrued Interest, Year Four, Originated, Three Years before Current Fiscal Year	0		0
Financing Receivable, Excluding Accrued Interest, Year Five, Originated, Four Years before Current Fiscal Year	0		0
Financing Receivable, Excluding Accrued Interest, Originated, More than Five Years before Current Fiscal Year	0		0
Financing Receivable, Excluding Accrued Interest, Revolving	100,000		100,000
Total	6,200,000		6,200,000
Agricultural
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Loan in Process	1,000,000.0		1,000,000.0		3,100,000
Nonaccrual loans	2,900,000		2,900,000		8,700,000
Less loans charged-off	0	0	0	5,400,000
Financing Receivable, Excluding Accrued Interest, Revolving, Converted to Term Loan	6,000,000.0		6,000,000.0
Financing Receivable, Excluding Accrued Interest, Year One, Originated, Current Fiscal Year	123,100,000		123,100,000		176,100,000
Financing Receivable, Excluding Accrued Interest, Year Two, Originated, Fiscal Year before Current Fiscal Year	76,600,000		76,600,000		67,600,000
Financing Receivable, Excluding Accrued Interest, Year Three, Originated, Two Years before Current Fiscal Year	38,100,000		38,100,000		35,000,000.0
Financing Receivable, Excluding Accrued Interest, Year Four, Originated, Three Years before Current Fiscal Year	27,100,000		27,100,000		12,200,000
Financing Receivable, Excluding Accrued Interest, Year Five, Originated, Four Years before Current Fiscal Year	8,400,000		8,400,000		10,100,000
Financing Receivable, Excluding Accrued Interest, Originated, More than Five Years before Current Fiscal Year	11,100,000		11,100,000		3,300,000
Financing Receivable, Excluding Accrued Interest, Revolving	400,100,000		400,100,000		402,100,000
Total	690,500,000		690,500,000		706,400,000
Agricultural | Pass
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Excluding Accrued Interest, Revolving, Converted to Term Loan	6,000,000.0		6,000,000.0
Financing Receivable, Excluding Accrued Interest, Year One, Originated, Current Fiscal Year	77,200,000		77,200,000		127,200,000
Financing Receivable, Excluding Accrued Interest, Year Two, Originated, Fiscal Year before Current Fiscal Year	74,800,000		74,800,000		59,700,000
Financing Receivable, Excluding Accrued Interest, Year Three, Originated, Two Years before Current Fiscal Year	35,900,000		35,900,000		31,800,000
Financing Receivable, Excluding Accrued Interest, Year Four, Originated, Three Years before Current Fiscal Year	25,500,000		25,500,000		10,600,000
Financing Receivable, Excluding Accrued Interest, Year Five, Originated, Four Years before Current Fiscal Year	7,700,000		7,700,000		8,600,000
Financing Receivable, Excluding Accrued Interest, Originated, More than Five Years before Current Fiscal Year	9,600,000		9,600,000		3,100,000
Financing Receivable, Excluding Accrued Interest, Revolving	374,000,000.0		374,000,000.0		375,100,000
Total	610,700,000		610,700,000		616,100,000
Agricultural | Other Assets Especially Mentioned
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Excluding Accrued Interest, Revolving, Converted to Term Loan	0		0
Financing Receivable, Excluding Accrued Interest, Year One, Originated, Current Fiscal Year	900,000		900,000		26,100,000
Financing Receivable, Excluding Accrued Interest, Year Two, Originated, Fiscal Year before Current Fiscal Year	1,100,000		1,100,000		2,800,000
Financing Receivable, Excluding Accrued Interest, Year Three, Originated, Two Years before Current Fiscal Year	800,000		800,000		400,000
Financing Receivable, Excluding Accrued Interest, Year Four, Originated, Three Years before Current Fiscal Year	200,000		200,000		1,000,000.0
Financing Receivable, Excluding Accrued Interest, Year Five, Originated, Four Years before Current Fiscal Year	200,000		200,000		300,000
Financing Receivable, Excluding Accrued Interest, Originated, More than Five Years before Current Fiscal Year	200,000		200,000		0
Financing Receivable, Excluding Accrued Interest, Revolving	9,700,000		9,700,000		26,200,000
Total	13,100,000		13,100,000		56,800,000
Agricultural | Substandard
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Excluding Accrued Interest, Revolving, Converted to Term Loan	0		0
Financing Receivable, Excluding Accrued Interest, Year One, Originated, Current Fiscal Year	45,000,000.0		45,000,000.0		22,800,000
Financing Receivable, Excluding Accrued Interest, Year Two, Originated, Fiscal Year before Current Fiscal Year	700,000		700,000		4,600,000
Financing Receivable, Excluding Accrued Interest, Year Three, Originated, Two Years before Current Fiscal Year	1,400,000		1,400,000		2,800,000
Financing Receivable, Excluding Accrued Interest, Year Four, Originated, Three Years before Current Fiscal Year	1,400,000		1,400,000		600,000
Financing Receivable, Excluding Accrued Interest, Year Five, Originated, Four Years before Current Fiscal Year	500,000		500,000		1,200,000
Financing Receivable, Excluding Accrued Interest, Originated, More than Five Years before Current Fiscal Year	1,300,000		1,300,000		200,000
Financing Receivable, Excluding Accrued Interest, Revolving	16,400,000		16,400,000		800,000
Total	66,700,000		66,700,000		33,000,000.0
Agricultural | Doubtful
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Excluding Accrued Interest, Year One, Originated, Current Fiscal Year					0
Financing Receivable, Excluding Accrued Interest, Year Two, Originated, Fiscal Year before Current Fiscal Year					500,000
Financing Receivable, Excluding Accrued Interest, Year Three, Originated, Two Years before Current Fiscal Year					0
Financing Receivable, Excluding Accrued Interest, Year Four, Originated, Three Years before Current Fiscal Year					0
Financing Receivable, Excluding Accrued Interest, Year Five, Originated, Four Years before Current Fiscal Year					0
Financing Receivable, Excluding Accrued Interest, Originated, More than Five Years before Current Fiscal Year					0
Financing Receivable, Excluding Accrued Interest, Revolving					0
Total					500,000
Other, including overdrafts
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Loan in Process	0		0		0
Nonaccrual loans	0		0		0
Loans And Leases Held For Investment [Member]
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Loan in Process	54,400,000		54,400,000		68,800,000
Nonaccrual loans	81,400,000		81,400,000		59,200,000
Non-owner occupied
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Less loans charged-off		100,000		3,000,000.0
Financing Receivable, Excluding Accrued Interest, Year One, Originated, Current Fiscal Year					1,163,700,000
Financing Receivable, Excluding Accrued Interest, Year Two, Originated, Fiscal Year before Current Fiscal Year					882,000,000.0
Financing Receivable, Excluding Accrued Interest, Year Three, Originated, Two Years before Current Fiscal Year					674,200,000
Financing Receivable, Excluding Accrued Interest, Year Four, Originated, Three Years before Current Fiscal Year					490,400,000
Financing Receivable, Excluding Accrued Interest, Year Five, Originated, Four Years before Current Fiscal Year					261,100,000
Financing Receivable, Excluding Accrued Interest, Originated, More than Five Years before Current Fiscal Year					907,600,000
Financing Receivable, Excluding Accrued Interest, Revolving					29,200,000
Total					4,408,200,000
Non-owner occupied | Pass
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Excluding Accrued Interest, Year One, Originated, Current Fiscal Year					1,162,600,000
Financing Receivable, Excluding Accrued Interest, Year Two, Originated, Fiscal Year before Current Fiscal Year					861,300,000
Financing Receivable, Excluding Accrued Interest, Year Three, Originated, Two Years before Current Fiscal Year					661,100,000
Financing Receivable, Excluding Accrued Interest, Year Four, Originated, Three Years before Current Fiscal Year					467,600,000
Financing Receivable, Excluding Accrued Interest, Year Five, Originated, Four Years before Current Fiscal Year					241,500,000
Financing Receivable, Excluding Accrued Interest, Originated, More than Five Years before Current Fiscal Year					890,400,000
Financing Receivable, Excluding Accrued Interest, Revolving					29,200,000
Total					4,313,700,000
Non-owner occupied | Other Assets Especially Mentioned
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Excluding Accrued Interest, Year One, Originated, Current Fiscal Year					1,000,000.0
Financing Receivable, Excluding Accrued Interest, Year Two, Originated, Fiscal Year before Current Fiscal Year					6,800,000
Financing Receivable, Excluding Accrued Interest, Year Three, Originated, Two Years before Current Fiscal Year					2,300,000
Financing Receivable, Excluding Accrued Interest, Year Four, Originated, Three Years before Current Fiscal Year					4,600,000
Financing Receivable, Excluding Accrued Interest, Year Five, Originated, Four Years before Current Fiscal Year					0
Financing Receivable, Excluding Accrued Interest, Originated, More than Five Years before Current Fiscal Year					7,400,000
Financing Receivable, Excluding Accrued Interest, Revolving					0
Total					22,100,000
Non-owner occupied | Substandard
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Excluding Accrued Interest, Year One, Originated, Current Fiscal Year					100,000
Financing Receivable, Excluding Accrued Interest, Year Two, Originated, Fiscal Year before Current Fiscal Year					13,900,000
Financing Receivable, Excluding Accrued Interest, Year Three, Originated, Two Years before Current Fiscal Year					10,800,000
Financing Receivable, Excluding Accrued Interest, Year Four, Originated, Three Years before Current Fiscal Year					18,200,000
Financing Receivable, Excluding Accrued Interest, Year Five, Originated, Four Years before Current Fiscal Year					19,600,000
Financing Receivable, Excluding Accrued Interest, Originated, More than Five Years before Current Fiscal Year					9,800,000
Financing Receivable, Excluding Accrued Interest, Revolving					0
Total					72,400,000
Owner occupied
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Less loans charged-off		0		2,200,000
Financing Receivable, Excluding Accrued Interest, Year One, Originated, Current Fiscal Year					812,700,000
Financing Receivable, Excluding Accrued Interest, Year Two, Originated, Fiscal Year before Current Fiscal Year					737,300,000
Financing Receivable, Excluding Accrued Interest, Year Three, Originated, Two Years before Current Fiscal Year					548,500,000
Financing Receivable, Excluding Accrued Interest, Year Four, Originated, Three Years before Current Fiscal Year					281,300,000
Financing Receivable, Excluding Accrued Interest, Year Five, Originated, Four Years before Current Fiscal Year					179,900,000
Financing Receivable, Excluding Accrued Interest, Originated, More than Five Years before Current Fiscal Year					574,000,000.0
Financing Receivable, Excluding Accrued Interest, Revolving					19,800,000
Total					3,153,500,000
Owner occupied | Pass
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Excluding Accrued Interest, Year One, Originated, Current Fiscal Year					793,000,000.0
Financing Receivable, Excluding Accrued Interest, Year Two, Originated, Fiscal Year before Current Fiscal Year					718,700,000
Financing Receivable, Excluding Accrued Interest, Year Three, Originated, Two Years before Current Fiscal Year					533,900,000
Financing Receivable, Excluding Accrued Interest, Year Four, Originated, Three Years before Current Fiscal Year					266,300,000
Financing Receivable, Excluding Accrued Interest, Year Five, Originated, Four Years before Current Fiscal Year					165,800,000
Financing Receivable, Excluding Accrued Interest, Originated, More than Five Years before Current Fiscal Year					551,300,000
Financing Receivable, Excluding Accrued Interest, Revolving					18,200,000
Total					3,047,200,000
Owner occupied | Other Assets Especially Mentioned
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Excluding Accrued Interest, Year One, Originated, Current Fiscal Year					10,900,000
Financing Receivable, Excluding Accrued Interest, Year Two, Originated, Fiscal Year before Current Fiscal Year					14,200,000
Financing Receivable, Excluding Accrued Interest, Year Three, Originated, Two Years before Current Fiscal Year					12,300,000
Financing Receivable, Excluding Accrued Interest, Year Four, Originated, Three Years before Current Fiscal Year					6,100,000
Financing Receivable, Excluding Accrued Interest, Year Five, Originated, Four Years before Current Fiscal Year					5,600,000
Financing Receivable, Excluding Accrued Interest, Originated, More than Five Years before Current Fiscal Year					5,500,000
Financing Receivable, Excluding Accrued Interest, Revolving					1,100,000
Total					55,700,000
Owner occupied | Substandard
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Excluding Accrued Interest, Year One, Originated, Current Fiscal Year					8,400,000
Financing Receivable, Excluding Accrued Interest, Year Two, Originated, Fiscal Year before Current Fiscal Year					3,000,000.0
Financing Receivable, Excluding Accrued Interest, Year Three, Originated, Two Years before Current Fiscal Year					2,300,000
Financing Receivable, Excluding Accrued Interest, Year Four, Originated, Three Years before Current Fiscal Year					8,900,000
Financing Receivable, Excluding Accrued Interest, Year Five, Originated, Four Years before Current Fiscal Year					8,500,000
Financing Receivable, Excluding Accrued Interest, Originated, More than Five Years before Current Fiscal Year					17,200,000
Financing Receivable, Excluding Accrued Interest, Revolving					500,000
Total					48,800,000
Owner occupied | Doubtful
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Excluding Accrued Interest, Year One, Originated, Current Fiscal Year					400,000
Financing Receivable, Excluding Accrued Interest, Year Two, Originated, Fiscal Year before Current Fiscal Year					1,400,000
Financing Receivable, Excluding Accrued Interest, Year Three, Originated, Two Years before Current Fiscal Year					0
Financing Receivable, Excluding Accrued Interest, Year Four, Originated, Three Years before Current Fiscal Year					0
Financing Receivable, Excluding Accrued Interest, Year Five, Originated, Four Years before Current Fiscal Year					0
Financing Receivable, Excluding Accrued Interest, Originated, More than Five Years before Current Fiscal Year					0
Financing Receivable, Excluding Accrued Interest, Revolving					0
Total					1,800,000
Multi-family
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Less loans charged-off		5,700,000		5,700,000
Financing Receivable, Excluding Accrued Interest, Year One, Originated, Current Fiscal Year					369,200,000
Financing Receivable, Excluding Accrued Interest, Year Two, Originated, Fiscal Year before Current Fiscal Year					204,900,000
Financing Receivable, Excluding Accrued Interest, Year Three, Originated, Two Years before Current Fiscal Year					189,000,000.0
Financing Receivable, Excluding Accrued Interest, Year Four, Originated, Three Years before Current Fiscal Year					52,100,000
Financing Receivable, Excluding Accrued Interest, Year Five, Originated, Four Years before Current Fiscal Year					35,000,000.0
Financing Receivable, Excluding Accrued Interest, Originated, More than Five Years before Current Fiscal Year					115,700,000
Financing Receivable, Excluding Accrued Interest, Revolving					1,000,000.0
Total					966,900,000
Multi-family | Pass
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Excluding Accrued Interest, Year One, Originated, Current Fiscal Year					369,200,000
Financing Receivable, Excluding Accrued Interest, Year Two, Originated, Fiscal Year before Current Fiscal Year					204,900,000
Financing Receivable, Excluding Accrued Interest, Year Three, Originated, Two Years before Current Fiscal Year					189,000,000.0
Financing Receivable, Excluding Accrued Interest, Year Four, Originated, Three Years before Current Fiscal Year					52,100,000
Financing Receivable, Excluding Accrued Interest, Year Five, Originated, Four Years before Current Fiscal Year					35,000,000.0
Financing Receivable, Excluding Accrued Interest, Originated, More than Five Years before Current Fiscal Year					113,700,000
Financing Receivable, Excluding Accrued Interest, Revolving					1,000,000.0
Total					964,900,000
Multi-family | Other Assets Especially Mentioned
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Excluding Accrued Interest, Year One, Originated, Current Fiscal Year					0
Financing Receivable, Excluding Accrued Interest, Year Two, Originated, Fiscal Year before Current Fiscal Year					0
Financing Receivable, Excluding Accrued Interest, Year Three, Originated, Two Years before Current Fiscal Year					0
Financing Receivable, Excluding Accrued Interest, Year Four, Originated, Three Years before Current Fiscal Year					0
Financing Receivable, Excluding Accrued Interest, Year Five, Originated, Four Years before Current Fiscal Year					0
Financing Receivable, Excluding Accrued Interest, Originated, More than Five Years before Current Fiscal Year					1,700,000
Financing Receivable, Excluding Accrued Interest, Revolving					0
Total					1,700,000
Multi-family | Substandard
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Excluding Accrued Interest, Year One, Originated, Current Fiscal Year					0
Financing Receivable, Excluding Accrued Interest, Year Two, Originated, Fiscal Year before Current Fiscal Year					0
Financing Receivable, Excluding Accrued Interest, Year Three, Originated, Two Years before Current Fiscal Year					0
Financing Receivable, Excluding Accrued Interest, Year Four, Originated, Three Years before Current Fiscal Year					0
Financing Receivable, Excluding Accrued Interest, Year Five, Originated, Four Years before Current Fiscal Year					0
Financing Receivable, Excluding Accrued Interest, Originated, More than Five Years before Current Fiscal Year					300,000
Financing Receivable, Excluding Accrued Interest, Revolving					0
Total					300,000
Commercial and floor plans
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Less loans charged-off		500,000		5,800,000
Financing Receivable, Excluding Accrued Interest, Year One, Originated, Current Fiscal Year					527,700,000
Financing Receivable, Excluding Accrued Interest, Year Two, Originated, Fiscal Year before Current Fiscal Year					370,300,000
Financing Receivable, Excluding Accrued Interest, Year Three, Originated, Two Years before Current Fiscal Year					219,400,000
Financing Receivable, Excluding Accrued Interest, Year Four, Originated, Three Years before Current Fiscal Year					132,100,000
Financing Receivable, Excluding Accrued Interest, Year Five, Originated, Four Years before Current Fiscal Year					124,400,000
Financing Receivable, Excluding Accrued Interest, Originated, More than Five Years before Current Fiscal Year					178,100,000
Financing Receivable, Excluding Accrued Interest, Revolving					697,400,000
Total					2,249,400,000
Commercial and floor plans | Pass
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Excluding Accrued Interest, Year One, Originated, Current Fiscal Year					501,700,000
Financing Receivable, Excluding Accrued Interest, Year Two, Originated, Fiscal Year before Current Fiscal Year					358,900,000
Financing Receivable, Excluding Accrued Interest, Year Three, Originated, Two Years before Current Fiscal Year					214,400,000
Financing Receivable, Excluding Accrued Interest, Year Four, Originated, Three Years before Current Fiscal Year					124,300,000
Financing Receivable, Excluding Accrued Interest, Year Five, Originated, Four Years before Current Fiscal Year					120,300,000
Financing Receivable, Excluding Accrued Interest, Originated, More than Five Years before Current Fiscal Year					171,100,000
Financing Receivable, Excluding Accrued Interest, Revolving					631,600,000
Total					2,122,300,000
Commercial and floor plans | Other Assets Especially Mentioned
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Excluding Accrued Interest, Year One, Originated, Current Fiscal Year					15,900,000
Financing Receivable, Excluding Accrued Interest, Year Two, Originated, Fiscal Year before Current Fiscal Year					6,800,000
Financing Receivable, Excluding Accrued Interest, Year Three, Originated, Two Years before Current Fiscal Year					1,300,000
Financing Receivable, Excluding Accrued Interest, Year Four, Originated, Three Years before Current Fiscal Year					4,400,000
Financing Receivable, Excluding Accrued Interest, Year Five, Originated, Four Years before Current Fiscal Year					900,000
Financing Receivable, Excluding Accrued Interest, Originated, More than Five Years before Current Fiscal Year					4,900,000
Financing Receivable, Excluding Accrued Interest, Revolving					18,500,000
Total					52,700,000
Commercial and floor plans | Substandard
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Excluding Accrued Interest, Year One, Originated, Current Fiscal Year					9,800,000
Financing Receivable, Excluding Accrued Interest, Year Two, Originated, Fiscal Year before Current Fiscal Year					3,300,000
Financing Receivable, Excluding Accrued Interest, Year Three, Originated, Two Years before Current Fiscal Year					3,700,000
Financing Receivable, Excluding Accrued Interest, Year Four, Originated, Three Years before Current Fiscal Year					3,400,000
Financing Receivable, Excluding Accrued Interest, Year Five, Originated, Four Years before Current Fiscal Year					3,200,000
Financing Receivable, Excluding Accrued Interest, Originated, More than Five Years before Current Fiscal Year					2,100,000
Financing Receivable, Excluding Accrued Interest, Revolving					47,200,000
Total					72,700,000
Commercial and floor plans | Doubtful
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Excluding Accrued Interest, Year One, Originated, Current Fiscal Year					300,000
Financing Receivable, Excluding Accrued Interest, Year Two, Originated, Fiscal Year before Current Fiscal Year					1,300,000
Financing Receivable, Excluding Accrued Interest, Year Three, Originated, Two Years before Current Fiscal Year					0
Financing Receivable, Excluding Accrued Interest, Year Four, Originated, Three Years before Current Fiscal Year					0
Financing Receivable, Excluding Accrued Interest, Year Five, Originated, Four Years before Current Fiscal Year					0
Financing Receivable, Excluding Accrued Interest, Originated, More than Five Years before Current Fiscal Year					0
Financing Receivable, Excluding Accrued Interest, Revolving					100,000
Total					1,700,000
Commercial purpose secured by 1-4 family
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Less loans charged-off		$ 0		$ 0
Financing Receivable, Excluding Accrued Interest, Year One, Originated, Current Fiscal Year					192,000,000.0
Financing Receivable, Excluding Accrued Interest, Year Two, Originated, Fiscal Year before Current Fiscal Year					136,000,000.0
Financing Receivable, Excluding Accrued Interest, Year Three, Originated, Two Years before Current Fiscal Year					72,000,000.0
Financing Receivable, Excluding Accrued Interest, Year Four, Originated, Three Years before Current Fiscal Year					30,900,000
Financing Receivable, Excluding Accrued Interest, Year Five, Originated, Four Years before Current Fiscal Year					32,200,000
Financing Receivable, Excluding Accrued Interest, Originated, More than Five Years before Current Fiscal Year					40,900,000
Financing Receivable, Excluding Accrued Interest, Revolving					28,900,000
Total					532,900,000
Commercial purpose secured by 1-4 family | Pass
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Excluding Accrued Interest, Year One, Originated, Current Fiscal Year					191,700,000
Financing Receivable, Excluding Accrued Interest, Year Two, Originated, Fiscal Year before Current Fiscal Year					134,500,000
Financing Receivable, Excluding Accrued Interest, Year Three, Originated, Two Years before Current Fiscal Year					69,800,000
Financing Receivable, Excluding Accrued Interest, Year Four, Originated, Three Years before Current Fiscal Year					30,400,000
Financing Receivable, Excluding Accrued Interest, Year Five, Originated, Four Years before Current Fiscal Year					29,900,000
Financing Receivable, Excluding Accrued Interest, Originated, More than Five Years before Current Fiscal Year					39,500,000
Financing Receivable, Excluding Accrued Interest, Revolving					28,900,000
Total					524,700,000
Commercial purpose secured by 1-4 family | Other Assets Especially Mentioned
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Excluding Accrued Interest, Year One, Originated, Current Fiscal Year					100,000
Financing Receivable, Excluding Accrued Interest, Year Two, Originated, Fiscal Year before Current Fiscal Year					1,200,000
Financing Receivable, Excluding Accrued Interest, Year Three, Originated, Two Years before Current Fiscal Year					2,100,000
Financing Receivable, Excluding Accrued Interest, Year Four, Originated, Three Years before Current Fiscal Year					200,000
Financing Receivable, Excluding Accrued Interest, Year Five, Originated, Four Years before Current Fiscal Year					1,400,000
Financing Receivable, Excluding Accrued Interest, Originated, More than Five Years before Current Fiscal Year					200,000
Financing Receivable, Excluding Accrued Interest, Revolving					0
Total					5,200,000
Commercial purpose secured by 1-4 family | Substandard
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Excluding Accrued Interest, Year One, Originated, Current Fiscal Year					200,000
Financing Receivable, Excluding Accrued Interest, Year Two, Originated, Fiscal Year before Current Fiscal Year					300,000
Financing Receivable, Excluding Accrued Interest, Year Three, Originated, Two Years before Current Fiscal Year					100,000
Financing Receivable, Excluding Accrued Interest, Year Four, Originated, Three Years before Current Fiscal Year					300,000
Financing Receivable, Excluding Accrued Interest, Year Five, Originated, Four Years before Current Fiscal Year					900,000
Financing Receivable, Excluding Accrued Interest, Originated, More than Five Years before Current Fiscal Year					1,200,000
Financing Receivable, Excluding Accrued Interest, Revolving					0
Total					3,000,000.0
30 to 59 Days Past Due | Commercial real estate
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Loan in Process	1,200,000		1,200,000		5,600,000
30 to 59 Days Past Due | Total construction loans
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Loan in Process	6,500,000		6,500,000		10,400,000
30 to 59 Days Past Due | Residential
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Loan in Process	2,400,000		2,400,000		9,900,000
30 to 59 Days Past Due | Agricultural
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Loan in Process	400,000		400,000		1,100,000
30 to 59 Days Past Due | Total real estate
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Loan in Process	10,500,000		10,500,000		27,000,000.0
30 to 59 Days Past Due | Indirect consumer
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Loan in Process	6,400,000		6,400,000		9,300,000
30 to 59 Days Past Due | Direct and advance lines
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Loan in Process	600,000		600,000		800,000
30 to 59 Days Past Due | Credit card
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Loan in Process	600,000		600,000		800,000
30 to 59 Days Past Due | Total consumer loans
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Loan in Process	7,600,000		7,600,000		10,900,000
30 to 59 Days Past Due | Commercial
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Loan in Process	2,300,000		2,300,000		7,100,000
30 to 59 Days Past Due | Agricultural
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Loan in Process	700,000		700,000		800,000
30 to 59 Days Past Due | Other, including overdrafts
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Loan in Process	0		0		0
30 to 59 Days Past Due | Loans And Leases Held For Investment [Member]
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Loan in Process	21,100,000		21,100,000		45,800,000
60 to 89 Days Past Due | Commercial real estate
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Loan in Process	400,000		400,000		800,000
60 to 89 Days Past Due | Total construction loans
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Loan in Process	7,500,000		7,500,000		600,000
60 to 89 Days Past Due | Residential
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Loan in Process	1,800,000		1,800,000		2,100,000
60 to 89 Days Past Due | Agricultural
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Loan in Process	1,500,000		1,500,000		6,100,000
60 to 89 Days Past Due | Total real estate
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Loan in Process	11,200,000		11,200,000		9,600,000
60 to 89 Days Past Due | Indirect consumer
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Loan in Process	2,200,000		2,200,000		2,400,000
60 to 89 Days Past Due | Direct and advance lines
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Loan in Process	200,000		200,000		300,000
60 to 89 Days Past Due | Credit card
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Loan in Process	400,000		400,000		400,000
60 to 89 Days Past Due | Total consumer loans
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Loan in Process	2,800,000		2,800,000		3,100,000
60 to 89 Days Past Due | Commercial
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Loan in Process	16,100,000		16,100,000		1,700,000
60 to 89 Days Past Due | Agricultural
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Loan in Process	0		0		2,200,000
60 to 89 Days Past Due | Other, including overdrafts
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Loan in Process	0		0		0
60 to 89 Days Past Due | Loans And Leases Held For Investment [Member]
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Loan in Process	30,100,000		30,100,000		16,600,000
Equal to or Greater than 90 Days Past Due | Commercial real estate
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Loan in Process	0		0		1,100,000
Equal to or Greater than 90 Days Past Due | Total construction loans
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Loan in Process	500,000		500,000		600,000
Equal to or Greater than 90 Days Past Due | Residential
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Loan in Process	1,000,000.0		1,000,000.0		1,200,000
Equal to or Greater than 90 Days Past Due | Agricultural
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Loan in Process	0		0		0
Equal to or Greater than 90 Days Past Due | Total real estate
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Loan in Process	1,500,000		1,500,000		2,900,000
Equal to or Greater than 90 Days Past Due | Indirect consumer
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Loan in Process	400,000		400,000		600,000
Equal to or Greater than 90 Days Past Due | Direct and advance lines
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Loan in Process	0		0		100,000
Equal to or Greater than 90 Days Past Due | Credit card
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Loan in Process	500,000		500,000		600,000
Equal to or Greater than 90 Days Past Due | Total consumer loans
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Loan in Process	900,000		900,000		1,300,000
Equal to or Greater than 90 Days Past Due | Commercial
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Loan in Process	500,000		500,000		2,100,000
Equal to or Greater than 90 Days Past Due | Agricultural
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Loan in Process	300,000		300,000		100,000
Equal to or Greater than 90 Days Past Due | Other, including overdrafts
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Loan in Process	0		0		0
Equal to or Greater than 90 Days Past Due | Loans And Leases Held For Investment [Member]
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Loan in Process	3,200,000		3,200,000		6,400,000
Financial Asset, Not Past Due | Commercial real estate
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Loan in Process	8,733,600,000		8,733,600,000		8,501,500,000
Financial Asset, Not Past Due | Total construction loans
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Loan in Process	1,898,400,000		1,898,400,000		1,929,100,000
Financial Asset, Not Past Due | Residential
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Loan in Process	2,197,500,000		2,197,500,000		2,168,700,000
Financial Asset, Not Past Due | Agricultural
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Loan in Process	724,200,000		724,200,000		780,100,000
Financial Asset, Not Past Due | Total real estate
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Loan in Process	13,553,700,000		13,553,700,000		13,379,400,000
Financial Asset, Not Past Due | Indirect consumer
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Loan in Process	739,700,000		739,700,000		814,700,000
Financial Asset, Not Past Due | Direct and advance lines
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Loan in Process	141,300,000		141,300,000		151,400,000
Financial Asset, Not Past Due | Credit card
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Loan in Process	70,100,000		70,100,000		74,100,000
Financial Asset, Not Past Due | Total consumer loans
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Loan in Process	951,100,000		951,100,000		1,040,200,000
Financial Asset, Not Past Due | Commercial
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Loan in Process	2,894,200,000		2,894,200,000		2,861,500,000
Financial Asset, Not Past Due | Agricultural
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Loan in Process	686,600,000		686,600,000		696,500,000
Financial Asset, Not Past Due | Other, including overdrafts
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Loan in Process	5,000,000.0		5,000,000.0		9,200,000
Financial Asset, Not Past Due | Loans And Leases Held For Investment [Member]
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Loan in Process	$ 18,090,600,000		18,090,600,000		$ 17,986,800,000
Year One, Originated, Current Fiscal Year | Commercial real estate
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Less loans charged-off			1,700,000
Year One, Originated, Current Fiscal Year | Total construction loans
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Less loans charged-off			0
Year One, Originated, Current Fiscal Year | Residential
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Less loans charged-off			300,000
Year One, Originated, Current Fiscal Year | Agricultural
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Less loans charged-off			0
Year One, Originated, Current Fiscal Year | Indirect consumer
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Less loans charged-off			200,000
Year One, Originated, Current Fiscal Year | Direct and advance lines
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Less loans charged-off			100,000
Year One, Originated, Current Fiscal Year | Credit card
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Less loans charged-off			0
Year One, Originated, Current Fiscal Year | Commercial
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Less loans charged-off			0
Year One, Originated, Current Fiscal Year | Agricultural
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Less loans charged-off			0
Year Two, Originated, Fiscal Year Before Current Fiscal Year | Commercial real estate
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Less loans charged-off			300,000
Year Two, Originated, Fiscal Year Before Current Fiscal Year | Total construction loans
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Less loans charged-off			0
Year Two, Originated, Fiscal Year Before Current Fiscal Year | Residential
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Less loans charged-off			0
Year Two, Originated, Fiscal Year Before Current Fiscal Year | Agricultural
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Less loans charged-off			0
Year Two, Originated, Fiscal Year Before Current Fiscal Year | Indirect consumer
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Less loans charged-off			2,000,000.0
Year Two, Originated, Fiscal Year Before Current Fiscal Year | Direct and advance lines
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Less loans charged-off			300,000
Year Two, Originated, Fiscal Year Before Current Fiscal Year | Credit card
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Less loans charged-off			0
Year Two, Originated, Fiscal Year Before Current Fiscal Year | Commercial
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Less loans charged-off			300,000
Year Two, Originated, Fiscal Year Before Current Fiscal Year | Agricultural
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Less loans charged-off			0
Year Three, Originated, Two Years before Current Fiscal Year | Commercial real estate
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Less loans charged-off			1,700,000
Year Three, Originated, Two Years before Current Fiscal Year | Total construction loans
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Less loans charged-off			100,000
Year Three, Originated, Two Years before Current Fiscal Year | Residential
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Less loans charged-off			100,000
Year Three, Originated, Two Years before Current Fiscal Year | Agricultural
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Less loans charged-off			0
Year Three, Originated, Two Years before Current Fiscal Year | Indirect consumer
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Less loans charged-off			1,600,000
Year Three, Originated, Two Years before Current Fiscal Year | Direct and advance lines
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Less loans charged-off			200,000
Year Three, Originated, Two Years before Current Fiscal Year | Credit card
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Less loans charged-off			0
Year Three, Originated, Two Years before Current Fiscal Year | Commercial
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Less loans charged-off			300,000
Year Three, Originated, Two Years before Current Fiscal Year | Agricultural
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Less loans charged-off			0
Year Four, Originated, Three Years before Current Fiscal Year | Commercial real estate
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Less loans charged-off			2,600,000
Year Four, Originated, Three Years before Current Fiscal Year | Total construction loans
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Less loans charged-off			0
Year Four, Originated, Three Years before Current Fiscal Year | Residential
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Less loans charged-off			100,000
Year Four, Originated, Three Years before Current Fiscal Year | Agricultural
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Less loans charged-off			0
Year Four, Originated, Three Years before Current Fiscal Year | Indirect consumer
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Less loans charged-off			600,000
Year Four, Originated, Three Years before Current Fiscal Year | Direct and advance lines
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Less loans charged-off			300,000
Year Four, Originated, Three Years before Current Fiscal Year | Credit card
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Less loans charged-off			0
Year Four, Originated, Three Years before Current Fiscal Year | Commercial
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Less loans charged-off			400,000
Year Four, Originated, Three Years before Current Fiscal Year | Agricultural
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Less loans charged-off			0
Year Five, Originated, Four Years before Current Fiscal Year | Commercial real estate
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Less loans charged-off			0
Year Five, Originated, Four Years before Current Fiscal Year | Total construction loans
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Less loans charged-off			0
Year Five, Originated, Four Years before Current Fiscal Year | Residential
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Less loans charged-off			0
Year Five, Originated, Four Years before Current Fiscal Year | Agricultural
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Less loans charged-off			0
Year Five, Originated, Four Years before Current Fiscal Year | Indirect consumer
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Less loans charged-off			200,000
Year Five, Originated, Four Years before Current Fiscal Year | Direct and advance lines
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Less loans charged-off			100,000
Year Five, Originated, Four Years before Current Fiscal Year | Credit card
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Less loans charged-off			0
Year Five, Originated, Four Years before Current Fiscal Year | Commercial
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Less loans charged-off			100,000
Year Five, Originated, Four Years before Current Fiscal Year | Agricultural
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Less loans charged-off			0
Originated, More than Five Years before Current Fiscal Year | Commercial real estate
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Less loans charged-off			0
Originated, More than Five Years before Current Fiscal Year | Total construction loans
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Less loans charged-off			0
Originated, More than Five Years before Current Fiscal Year | Residential
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Less loans charged-off			100,000
Originated, More than Five Years before Current Fiscal Year | Agricultural
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Less loans charged-off			0
Originated, More than Five Years before Current Fiscal Year | Indirect consumer
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Less loans charged-off			600,000
Originated, More than Five Years before Current Fiscal Year | Direct and advance lines
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Less loans charged-off			2,100,000
Originated, More than Five Years before Current Fiscal Year | Credit card
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Less loans charged-off			0
Originated, More than Five Years before Current Fiscal Year | Commercial
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Less loans charged-off			100,000
Originated, More than Five Years before Current Fiscal Year | Agricultural
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Less loans charged-off			0
Revolving | Commercial real estate
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Less loans charged-off			0
Revolving | Total construction loans
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Less loans charged-off			0
Revolving | Residential
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Less loans charged-off			0
Revolving | Agricultural
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Less loans charged-off			0
Revolving | Indirect consumer
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Less loans charged-off			0
Revolving | Direct and advance lines
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Less loans charged-off			100,000
Revolving | Credit card
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Less loans charged-off			2,000,000.0
Revolving | Commercial
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Less loans charged-off			900,000
Revolving | Agricultural
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Less loans charged-off			0
Revolving, Converted to Term | Commercial real estate
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Less loans charged-off			0
Revolving, Converted to Term | Total construction loans
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Less loans charged-off			9,600,000
Revolving, Converted to Term | Residential
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Less loans charged-off			0
Revolving, Converted to Term | Agricultural
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Less loans charged-off			0
Revolving, Converted to Term | Indirect consumer
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Less loans charged-off			0
Revolving, Converted to Term | Direct and advance lines
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Less loans charged-off			0
Revolving, Converted to Term | Credit card
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Less loans charged-off			0
Revolving, Converted to Term | Commercial
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Less loans charged-off			100,000
Revolving, Converted to Term | Agricultural
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]
Less loans charged-off			$ 0