Commitments and Contingencies (Outstanding Financial Instruments Contract Amounts Represent Credit Risk) (Detail) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Loss Contingencies [Line Items]
Unused Commitments to Extend Credit	$ 7,152,331	$ 6,755,563
Standby letters of credit [Member]
Loss Contingencies [Line Items]
Unused Commitments to Extend Credit	224,061	207,201
Letter of Credit [Member]
Loss Contingencies [Line Items]
Unused Commitments to Extend Credit	58,175	30,522
Commitments to extend credit [Member]
Loss Contingencies [Line Items]
Unused Commitments to Extend Credit	$ 6,870,095	$ 6,517,840