Off-Balance Sheet Arrangements Commitments Guarantees and Contingencies (Narrative) (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Commitments And Guarantees [Line Items]
Credit card guarantees	$ 8,600	$ 9,100
Fully collateralized credit card guarantees	962	8,200
Frost Wealth Advisors [Member]
Commitments And Guarantees [Line Items]
Fair value of off-balance sheet managed and custody assets	$ 43,300,000	$ 38,600,000	$ 37,800,000