Loans and Allowance for Credit Losses - Rollforward of Allowance for Credit/Loan Losses by Portfolio Segment (Detail) - USD ($)		3 Months Ended
	Jan. 31, 2025	Mar. 31, 2025	Mar. 31, 2024
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning balance		$ 261,734,000	$ 222,996,000
PCD allowance for credit loss at acquisition	$ 62,126,000	62,126,000
Charge-offs		(36,967,000)	(5,477,000)
Recoveries		1,095,000	2,460,000
Provision		85,500,000	10,000,000
Ending balance - ACL		373,488,000	229,979,000
Beginning balance - ACL on off-balance sheet		4,138,000	5,088,000
Initial allowance for credit loss at acquisition		3,583,000
Provision		500,000	0
Ending balance - ACL on off-balance sheet		8,221,000	5,088,000
Commercial and Industrial Portfolio [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning balance		160,912,000	155,658,000
PCD allowance for credit loss at acquisition		35,143,000
Charge-offs		(25,996,000)	(944,000)
Recoveries		69,000	1,252,000
Provision		22,018,000	(16,142,000)
Ending balance - ACL		192,146,000	139,824,000
Beginning balance - ACL on off-balance sheet		2,083,000	4,092,000
Initial allowance for credit loss at acquisition		2,166,000
Provision		1,226,000
Ending balance - ACL on off-balance sheet		5,475,000	4,092,000
Specialty Lending Portfolio [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recoveries			1,000
Provision			(1,000)
Beginning balance - ACL on off-balance sheet			186,000
Ending balance - ACL on off-balance sheet			186,000
Commercial Real Estate Portfolio [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning balance		77,340,000	45,507,000
PCD allowance for credit loss at acquisition		26,764,000
Charge-offs		(2,324,000)	(250,000)
Provision		47,565,000	21,034,000
Ending balance - ACL		149,345,000	66,291,000
Beginning balance - ACL on off-balance sheet		1,741,000	460,000
Initial allowance for credit loss at acquisition		1,192,000
Provision		(521,000)
Ending balance - ACL on off-balance sheet		2,412,000	460,000
Consumer Real Estate Portfolio [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning balance		4,327,000	6,941,000
PCD allowance for credit loss at acquisition		206,000
Charge-offs		(1,229,000)	(174,000)
Recoveries		16,000	606,000
Provision		1,478,000	(3,974,000)
Ending balance - ACL		4,798,000	3,399,000
Beginning balance - ACL on off-balance sheet		70,000	117,000
Initial allowance for credit loss at acquisition		63,000
Provision		5,000
Ending balance - ACL on off-balance sheet		138,000	117,000
Consumer Portfolio [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning balance		966,000	1,089,000
PCD allowance for credit loss at acquisition		13,000
Charge-offs		(742,000)	(408,000)
Recoveries		119,000	76,000
Provision		1,132,000	(226,000)
Ending balance - ACL		1,488,000	531,000
Beginning balance - ACL on off-balance sheet		16,000	9,000
Initial allowance for credit loss at acquisition		41,000
Provision		34,000
Ending balance - ACL on off-balance sheet		91,000	9,000
Credit Cards Portfolio [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning balance		14,272,000	7,935,000
Charge-offs		(6,676,000)	(3,701,000)
Recoveries		891,000	525,000
Provision		11,508,000	9,798,000
Ending balance - ACL		19,995,000	14,557,000
Leases and Other Portfolio [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning balance		1,272,000	2,608,000
Provision		(122,000)	(1,051,000)
Ending balance - ACL		1,150,000	1,557,000
Beginning balance - ACL on off-balance sheet		214,000	160,000
Initial allowance for credit loss at acquisition		114,000
Provision		(233,000)
Ending balance - ACL on off-balance sheet		95,000	160,000
Total - Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning balance		259,089,000	219,738,000
PCD allowance for credit loss at acquisition		62,126,000
Charge-offs		(36,967,000)	(5,477,000)
Recoveries		1,095,000	2,460,000
Provision		83,579,000	9,438,000
Ending balance - ACL		368,922,000	226,159,000
Beginning balance - ACL on off-balance sheet		4,124,000	5,024,000
Initial allowance for credit loss at acquisition		3,576,000
Provision		511,000
Ending balance - ACL on off-balance sheet		8,211,000	5,024,000
HTM [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning balance		2,645,000	3,258,000
Provision		1,921,000	562,000
Ending balance - ACL		4,566,000	3,820,000
Beginning balance - ACL on off-balance sheet		14,000	64,000
Initial allowance for credit loss at acquisition		7,000
Provision		(11,000)
Ending balance - ACL on off-balance sheet		$ 10,000	$ 64,000