Loans and Leases and the Allowance for Credit Losses - Summary of Current, Past Due and Nonaccrual Loans (Detail) - USD ($) $ in Thousands		Mar. 31, 2025	Dec. 31, 2024	Mar. 31, 2024	Jan. 01, 2024	Jan. 01, 2023
Financing Receivable, Past Due [Line Items]
Amortized Cost		$ 1,540,000	$ 1,690,000	$ 2,302,000	$ 1,690,000	$ 2,166,000
Total (a) (b)	[1]	134,574,000	135,581,000
Current
Financing Receivable, Past Due [Line Items]
Loans		131,203,000	131,898,000
30-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Loans		1,447,000	1,655,000
Accruing Loans Past Due 90 Days or More
Financing Receivable, Past Due [Line Items]
Loans		384,000	338,000
Commercial and industrial
Financing Receivable, Past Due [Line Items]
Amortized Cost		662,000	696,000	864,000	696,000	670,000
Total (a) (b)		60,596,000	61,481,000
Commercial and industrial | Current
Financing Receivable, Past Due [Line Items]
Loans		59,671,000	60,374,000
Commercial and industrial | 30-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Loans		256,000	399,000
Commercial and industrial | Accruing Loans Past Due 90 Days or More
Financing Receivable, Past Due [Line Items]
Loans		7,000	12,000
Commercial Real Estate | Commercial
Financing Receivable, Past Due [Line Items]
Amortized Cost		394,000	468,000	855,000	468,000	869,000
Total (a) (b)		20,096,000	20,780,000
Commercial Real Estate | Commercial | Current
Financing Receivable, Past Due [Line Items]
Loans		19,351,000	20,054,000
Commercial Real Estate | Commercial | 30-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Loans		351,000	255,000
Commercial Real Estate | Commercial | Accruing Loans Past Due 90 Days or More
Financing Receivable, Past Due [Line Items]
Loans		0	3,000
Commercial Real Estate | Residential builder and developer
Financing Receivable, Past Due [Line Items]
Amortized Cost		1,000	2,000	3,000	2,000	3,000
Total (a) (b)		826,000	835,000
Commercial Real Estate | Residential builder and developer | Current
Financing Receivable, Past Due [Line Items]
Loans		819,000	830,000
Commercial Real Estate | Residential builder and developer | 30-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Loans		6,000	3,000
Commercial Real Estate | Residential builder and developer | Accruing Loans Past Due 90 Days or More
Financing Receivable, Past Due [Line Items]
Loans		0	0
Commercial Real Estate | Other commercial construction
Financing Receivable, Past Due [Line Items]
Amortized Cost		28,000	66,000	141,000	66,000	171,000
Total (a) (b)		4,945,000	5,149,000
Commercial Real Estate | Other commercial construction | Current
Financing Receivable, Past Due [Line Items]
Loans		4,867,000	5,018,000
Commercial Real Estate | Other commercial construction | 30-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Loans		50,000	65,000
Commercial Real Estate | Other commercial construction | Accruing Loans Past Due 90 Days or More
Financing Receivable, Past Due [Line Items]
Loans		0	0
Residential Real Estate | Residential
Financing Receivable, Past Due [Line Items]
Amortized Cost		284,000	279,000	255,000	279,000	270,000
Total (a) (b)		23,284,000	23,166,000
Residential Real Estate | Residential | Current
Financing Receivable, Past Due [Line Items]
Loans		22,053,000	21,853,000
Total (a) (b)		22,053,000	21,853,000
Residential Real Estate | Residential | 30-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Loans		579,000	719,000
Residential Real Estate | Residential | Accruing Loans Past Due 90 Days or More
Financing Receivable, Past Due [Line Items]
Loans		368,000	315,000
Total (a) (b)		368,000	315,000
Consumer: | Home equity lines and loans
Financing Receivable, Past Due [Line Items]
Amortized Cost		78,000	81,000	87,000	81,000	81,000
Total (a) (b)		4,556,000	4,592,000
Consumer: | Home equity lines and loans | Current
Financing Receivable, Past Due [Line Items]
Loans		4,450,000	4,482,000
Total (a) (b)		4,450,000	4,482,000
Consumer: | Home equity lines and loans | 30-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Loans		28,000	29,000
Consumer: | Home equity lines and loans | Accruing Loans Past Due 90 Days or More
Financing Receivable, Past Due [Line Items]
Loans		0	0
Total (a) (b)		0	0
Consumer: | Recreational finance
Financing Receivable, Past Due [Line Items]
Amortized Cost		26,000	31,000	30,000	31,000	36,000
Total (a) (b)		12,913,000	12,564,000
Consumer: | Recreational finance | Current
Financing Receivable, Past Due [Line Items]
Loans		12,794,000	12,429,000
Total (a) (b)		12,794,000	12,429,000
Consumer: | Recreational finance | 30-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Loans		93,000	104,000
Consumer: | Recreational finance | Accruing Loans Past Due 90 Days or More
Financing Receivable, Past Due [Line Items]
Loans		0	0
Total (a) (b)		0	0
Consumer: | Automobile
Financing Receivable, Past Due [Line Items]
Amortized Cost		11,000	12,000	13,000	12,000	14,000
Total (a) (b)		5,127,000	4,794,000
Consumer: | Automobile | Current
Financing Receivable, Past Due [Line Items]
Loans		5,064,000	4,724,000
Total (a) (b)		5,064,000	4,724,000
Consumer: | Automobile | 30-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Loans		52,000	58,000
Consumer: | Automobile | Accruing Loans Past Due 90 Days or More
Financing Receivable, Past Due [Line Items]
Loans		0	0
Total (a) (b)		0	0
Consumer: | Other
Financing Receivable, Past Due [Line Items]
Amortized Cost		56,000	55,000	$ 54,000	$ 55,000	$ 52,000
Total (a) (b)		2,231,000	2,220,000
Consumer: | Other | Current
Financing Receivable, Past Due [Line Items]
Loans		2,134,000	2,134,000
Consumer: | Other | 30-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Loans		32,000	23,000
Consumer: | Other | Accruing Loans Past Due 90 Days or More
Financing Receivable, Past Due [Line Items]
Loans		$ 9,000	$ 8,000

[1] Loans and leases of $2.1 billion and $1.5 billion at March 31, 2025 and December 31, 2024, respectively, were held in special purpose trusts to settle the respective obligations of asset-backed notes issued by those trusts. The outstanding balances of those asset-backed notes were included in Long-term borrowings and were $1.8 billion at March 31, 2025 and $1.2 billion at December 31, 2024.