Commitments and Contingencies - Contractual Commitments for Lines and Letters of Credit by Maturity (Detail) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Loss Contingencies [Line Items]
Total Amount Committed	$ 13,900.7	$ 9,903.6
Other Commitment, Due in Next Twelve Months	4,149.0
Other Commitment, Due in Second and Third Year	6,238.1
Other Commitment, Due in Fourth and Fifth Year	2,326.5
Other Commitment, Due after Fifth Year	1,187.0
Commitments to extend credit [Member]
Loss Contingencies [Line Items]
Total Amount Committed	13,396.3	9,425.2
Other Commitment, Due in Next Twelve Months	3,652.0
Other Commitment, Due in Second and Third Year	6,235.1
Other Commitment, Due in Fourth and Fifth Year	2,322.1
Other Commitment, Due after Fifth Year	1,187.0
Credit card guarantees [Member]
Loss Contingencies [Line Items]
Total Amount Committed	306.3	291.5
Other Commitment, Due in Next Twelve Months	306.3
Other Commitment, Due in Second and Third Year	0.0
Other Commitment, Due in Fourth and Fifth Year	0.0
Other Commitment, Due after Fifth Year	0.0
Standby letters of credit [Member]
Loss Contingencies [Line Items]
Total Amount Committed	198.1	$ 186.9
Other Commitment, Due in Next Twelve Months	190.7
Other Commitment, Due in Second and Third Year	3.0
Other Commitment, Due in Fourth and Fifth Year	4.4
Other Commitment, Due after Fifth Year	$ 0.0