Fair Value Measurements (Narrative) (Detail) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2022	Sep. 30, 2022	Sep. 30, 2021	Dec. 31, 2021
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Remaining unfunded commitment	$ 1,193	$ 1,193		$ 5,975
Unused commitments to extend credit	11,249,612	11,249,612		$ 7,152,331
Transfer of loans and leases to loans-held-for-sale		621,922	$ 74,923
Loans in process of foreclosure	9,700	9,700
Fair Value, Nonrecurring
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Other assets	2,100	2,100
Rabbi Trust
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Other assets	10,300	10,300
Alternative investments
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Other assets	76,100	76,100
Carrying amount of alternative investments	500	500
Remaining unfunded commitment	0	0
Write-down	200	1,400
Alternative investments carrying amount	75,200	75,200
Alternative investments | Fair Value, Nonrecurring
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Unused commitments to extend credit	31,100	31,100
Unused commitments to extend credit, written up	$ 500	$ 500