Business Combinations - Additional Information (Detail) - MUFG Union Bank [Member] - Forecast [Member] $ in Billions	6 Months Ended
	Jun. 30, 2022 USD ($) Branches shares
Business Acquisition [Line Items]
Business combination, Consideration transferred	$ 8.0
Payments to acquire businesses, gross	$ 5.5
Business acquisition, Percentage of voting interests acquired	2.90%
Business combination, Recognized identifiable assets acquired and liabilities assumed, Assets	$ 105.0
Business combination, Recognized identifiable assets acquired and liabilities assumed, Financial liabilities	58.0
Business combination, Recognized identifiable assets acquired and liabilities assumed, Deposits	$ 90.0
Number of branches acquired | Branches	300
Common Stock [Member]
Business Acquisition [Line Items]
Business acquisition, Equity interest issued or issuable, Number of shares | shares	44,000,000