Reporting Segments (Results of Reporting Segments) (Details) $ in Millions	3 Months Ended						9 Months Ended
	Sep. 30, 2022 USD ($)	Jun. 30, 2022 USD ($)	Mar. 31, 2022 USD ($)	Sep. 30, 2021 USD ($)	Jun. 30, 2021 USD ($)	Mar. 31, 2021 USD ($)	Sep. 30, 2022 USD ($) segment	Sep. 30, 2021 USD ($)
Segment Reporting Information [Line Items]
Number of reporting segments | segment							2
Noninterest Income
Trust, Investment and Other Servicing Fees	$ 1,078.7			$ 1,111.0			$ 3,390.5	$ 3,250.1
Foreign Exchange Trading Income	64.7			66.4			223.2	215.7
Other Noninterest Income	98.4			110.0			275.8	309.6
Total Noninterest Income	1,241.8			1,287.4			3,889.5	3,775.4
Net Interest Income	513.0			346.4			1,352.7	1,022.1
Revenue	1,754.8			1,633.8			5,242.2	4,797.5
Provision for Credit Losses	0.5			(13.0)			7.0	(70.0)
Noninterest Expense	1,229.8			1,128.7			3,659.3	3,367.0
Income before Income Taxes	524.5			518.1			1,575.9	1,500.5
Provision for Income Taxes	129.7			122.4			395.6	361.6
Net Income	$ 394.8	$ 396.2	$ 389.3	$ 395.7	$ 368.1	$ 375.1	$ 1,180.3	$ 1,138.9
Percentage of Consolidated Net Income	100.00%			100.00%			100.00%	100.00%
Average Assets	$ 146,402.2			$ 156,452.8			$ 154,152.1	$ 154,681.3
RECONCILING ITEMS
Noninterest Income
Trust, Investment and Other Servicing Fees	0.0			0.0			0.0	0.0
Foreign Exchange Trading Income	0.0			0.0			0.0	0.0
Other Noninterest Income	0.0			0.0			0.0	0.0
Total Noninterest Income	0.0			0.0			0.0	0.0
Net Interest Income	(12.3)			(10.7)			(30.1)	(25.6)
Revenue	(12.3)			(10.7)			(30.1)	(25.6)
Provision for Credit Losses	0.0			0.0			0.0	0.0
Noninterest Expense	0.0			0.0			0.0	0.0
Income before Income Taxes	(12.3)			(10.7)			(30.1)	(25.6)
Provision for Income Taxes	(12.3)			(10.7)			(30.1)	(25.6)
Net Income	0.0			0.0			0.0	0.0
OTHER
Noninterest Income
Trust, Investment and Other Servicing Fees	0.0			0.0			0.0	0.0
Foreign Exchange Trading Income	0.0			0.0			0.0	0.0
Other Noninterest Income	(1.1)			(3.6)			(11.2)	(15.7)
Total Noninterest Income	(1.1)			(3.6)			(11.2)	(15.7)
Net Interest Income	0.0			0.0			0.0	0.0
Revenue	(1.1)			(3.6)			(11.2)	(15.7)
Provision for Credit Losses	0.0			0.0			0.0	0.0
Noninterest Expense	20.4			1.2			56.7	21.2
Income before Income Taxes	(21.5)			(4.8)			(67.9)	(36.9)
Provision for Income Taxes	(5.3)			(1.2)			(16.9)	(9.2)
Net Income	$ (16.2)			$ (3.6)			$ (51.0)	$ (27.7)
Percentage of Consolidated Net Income	(4.00%)			(1.00%)			(4.00%)	(2.00%)
Average Assets	$ 0.0			$ 0.0			$ 0.0	$ 0.0
ASSET SERVICING | Operating Segments
Noninterest Income
Trust, Investment and Other Servicing Fees	603.2			630.2			1,908.4	1,862.2
Foreign Exchange Trading Income	63.7			63.2			215.9	205.6
Other Noninterest Income	62.5			65.6			185.4	194.8
Total Noninterest Income	729.4			759.0			2,309.7	2,262.6
Net Interest Income	303.3			158.9			748.5	472.7
Revenue	1,032.7			917.9			3,058.2	2,735.3
Provision for Credit Losses	(5.1)			(6.9)			3.8	(29.1)
Noninterest Expense	760.4			716.6			2,269.4	2,133.3
Income before Income Taxes	277.4			208.2			785.0	631.1
Provision for Income Taxes	67.7			50.0			194.0	153.1
Net Income	$ 209.7			$ 158.2			$ 591.0	$ 478.0
Percentage of Consolidated Net Income	53.00%			40.00%			50.00%	42.00%
Average Assets	$ 109,677.2			$ 119,951.9			$ 117,251.0	$ 119,859.4
WEALTH MANAGEMENT | Operating Segments
Noninterest Income
Trust, Investment and Other Servicing Fees	475.5			480.8			1,482.1	1,387.9
Foreign Exchange Trading Income	1.0			3.2			7.3	10.1
Other Noninterest Income	37.0			48.0			101.6	130.5
Total Noninterest Income	513.5			532.0			1,591.0	1,528.5
Net Interest Income	222.0			198.2			634.3	575.0
Revenue	735.5			730.2			2,225.3	2,103.5
Provision for Credit Losses	5.6			(6.1)			3.2	(40.9)
Noninterest Expense	449.0			410.9			1,333.2	1,212.5
Income before Income Taxes	280.9			325.4			888.9	931.9
Provision for Income Taxes	79.6			84.3			248.6	243.3
Net Income	$ 201.3			$ 241.1			$ 640.3	$ 688.6
Percentage of Consolidated Net Income	51.00%			61.00%			54.00%	60.00%
Average Assets	$ 36,725.0			$ 36,500.9			$ 36,901.1	$ 34,821.9