Fair Value Measurements - Narrative (Detail) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024	Dec. 31, 2024
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Broker dealer deposit program fair value		$ 2,500,000
Total credit-related financial instruments with off-balance sheet risk		12,921,970		$ 12,237,964
Total write-ups		1,800
Proceeds from sales of alternative investments		9,536	$ 0
Gains on sale		5,748	$ 0
Loans transferred to held-for-sale		278,300		27,300
Amortized cost of consumer loans		10,300
Fair Value, Nonrecurring
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments held in Rabbi Trust		2,500		400
Carrying amount of alternative investments		3,800
Proceeds from sales of alternative investments		9,500
Gains on sale		5,700
Rabbi Trust
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments held in Rabbi Trust		9,500		9,200
Alternative investments
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments held in Rabbi Trust		38,100		30,100
Readily determinable fair value proceeds	$ 1,200
Write-down of TDR's	$ 300
Equity investment, carrying amount		0		0
Alternative investments, carrying amount		50,500		43,400
Alternative investments | Fair Value, Nonrecurring
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total credit-related financial instruments with off-balance sheet risk		70,800		61,500
Alternative investments measured at fair value		$ 8,200		$ 8,300