Reporting Segments and Related Information - Information by Reporting Segment (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Noninterest Income
Trust, Investment and Other Servicing Fees	$ 4,727.8	$ 4,361.8	$ 4,432.6
Foreign Exchange Trading Income	231.2	203.9	288.6
Other Noninterest Income (Loss)	1,154.3	225.8	152.8
Total Noninterest Income	6,113.3	4,791.5	4,874.0
Net interest income	2,177.1	1,982.0	1,887.2
Revenue	8,290.4	6,773.5	6,761.2
Provision for Credit Losses	(3.0)	24.5	12.0
Compensation	2,471.1	2,321.8	2,248.0
Employee Benefits	417.8	405.2	437.4
Outside Services	998.0	906.5	880.3
Allocated Expense	0.0	0.0	0.0
Other Segment Items	1,747.0	1,650.7	1,417.2
Total Noninterest Expense	5,633.9	5,284.2	4,982.9
Income before Income Taxes	2,659.5	1,464.8	1,766.3
Provision for Income Taxes	628.4	357.5	430.3
NET INCOME	$ 2,031.1	$ 1,107.3	$ 1,336.0
Percentage of Consolidated Net Income	100.00%	100.00%	100.00%
Average Assets	$ 146,633.5	$ 142,649.2	$ 152,551.9
Average Loans	40,916.7	42,177.0	41,030.6
Average Deposits	112,700.3	105,245.5	125,592.4
Other
Noninterest Income
Trust, Investment and Other Servicing Fees	0.0	0.0	0.0
Foreign Exchange Trading Income	0.0	0.0	0.0
Other Noninterest Income (Loss)	742.1	(188.4)	(235.6)
Total Noninterest Income	742.1	(188.4)	(235.6)
Net interest income	(32.3)	(57.5)	(45.6)
Revenue	709.8	(245.9)	(281.2)
Provision for Credit Losses	(7.2)	0.0	0.0
Compensation	876.8	793.8	779.1
Employee Benefits	128.6	123.9	159.9
Outside Services	515.8	414.8	405.5
Allocated Expense	(2,863.0)	(2,594.9)	(2,454.0)
Other Segment Items	1,494.0	1,391.1	1,184.2
Total Noninterest Expense	152.2	128.7	74.7
Income before Income Taxes	564.8	(374.6)	(355.9)
Provision for Income Taxes	129.8	(75.5)	(122.9)
NET INCOME	$ 435.0	$ (299.1)	$ (233.0)
Percentage of Consolidated Net Income	21.00%	(27.00%)	(17.00%)
Average Assets	$ 366.8	$ 0.0	$ 0.0
Average Loans	0.0	0.0	0.0
Average Deposits	366.8	0.0	0.0
Asset Servicing segment | Operating Segments
Noninterest Income
Trust, Investment and Other Servicing Fees	2,632.8	2,461.9	2,496.3
Foreign Exchange Trading Income	247.2	213.0	281.0
Other Noninterest Income (Loss)	271.9	263.4	250.7
Total Noninterest Income	3,151.9	2,938.3	3,028.0
Net interest income	1,216.0	1,197.3	1,072.7
Revenue	4,367.9	4,135.6	4,100.7
Provision for Credit Losses	(4.6)	0.5	2.4
Compensation	1,016.3	970.2	948.5
Employee Benefits	201.5	197.1	190.7
Outside Services	437.0	449.8	433.5
Allocated Expense	1,660.5	1,469.5	1,344.8
Other Segment Items	175.4	186.6	175.2
Total Noninterest Expense	3,490.7	3,273.2	3,092.7
Income before Income Taxes	881.8	861.9	1,005.6
Provision for Income Taxes	193.7	187.1	243.2
NET INCOME	$ 688.1	$ 674.8	$ 762.4
Percentage of Consolidated Net Income	34.00%	61.00%	57.00%
Average Assets	$ 107,784.1	$ 101,472.6	$ 115,646.4
Average Loans	6,315.5	7,372.6	7,208.0
Average Deposits	86,775.3	81,812.6	96,166.1
Wealth Management segment | Operating Segments
Noninterest Income
Trust, Investment and Other Servicing Fees	2,095.0	1,899.9	1,936.3
Foreign Exchange Trading Income	(16.0)	(9.1)	7.6
Other Noninterest Income (Loss)	140.3	150.8	137.7
Total Noninterest Income	2,219.3	2,041.6	2,081.6
Net interest income	993.4	842.2	860.1
Revenue	3,212.7	2,883.8	2,941.7
Provision for Credit Losses	8.8	24.0	9.6
Compensation	578.0	557.8	520.4
Employee Benefits	87.7	84.2	86.8
Outside Services	45.2	41.9	41.3
Allocated Expense	1,202.5	1,125.4	1,109.2
Other Segment Items	77.6	73.0	57.8
Total Noninterest Expense	1,991.0	1,882.3	1,815.5
Income before Income Taxes	1,212.9	977.5	1,116.6
Provision for Income Taxes	304.9	245.9	310.0
NET INCOME	$ 908.0	$ 731.6	$ 806.6
Percentage of Consolidated Net Income	45.00%	66.00%	60.00%
Average Assets	$ 38,482.6	$ 41,176.6	$ 36,905.5
Average Loans	34,601.2	34,804.4	33,822.6
Average Deposits	$ 25,558.2	$ 23,432.9	$ 29,426.3