Reporting Segments (Results of Reporting Segments) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Segment Reporting Information [Line Items]
Trust, Investment and Other Servicing Fees	$ 848.2	$ 777.2	$ 1,656.4	$ 1,525.4
Foreign Exchange Trading Income	49.9	64.4	98.0	124.9
Other Noninterest Income	81.6	175.4	156.2	248.9
Net Interest Income	350.4	306.6	712.8	620.6
Revenue	1,330.1	1,323.6	2,623.4	2,519.8
Provision for Credit Losses	(7.0)	(3.0)	(8.0)	(1.0)
Noninterest Expense	937.4	925.0	1,831.9	1,753.8
Income before Income Taxes	399.7	401.6	799.5	767.0
Provision for Income Taxes	131.8	138.6	255.5	258.6
Net Income	$ 267.9	$ 263.0	$ 544.0	$ 508.4
Percentage of Consolidated Net Income	100.00%	100.00%	100.00%	100.00%
Average Assets	$ 118,400.7	$ 114,913.8	$ 117,443.8	$ 114,165.4
FTE adjustments	8.9	6.9	17.8	13.1
Corporate & Institutional Services
Segment Reporting Information [Line Items]
Trust, Investment and Other Servicing Fees	487.1	446.9	950.0	880.3
Foreign Exchange Trading Income	50.6	62.2	99.7	113.9
Other Noninterest Income	44.4	25.9	88.6	71.5
Net Interest Income	176.0	141.2	342.5	279.6
Revenue	758.1	676.2	1,480.8	1,345.3
Provision for Credit Losses	(2.7)	(0.8)	(2.4)	(4.0)
Noninterest Expense	545.6	556.8	1,056.4	1,032.1
Income before Income Taxes	215.2	120.2	426.8	317.2
Provision for Income Taxes	67.7	34.0	134.6	96.2
Net Income	$ 147.5	$ 86.2	$ 292.2	$ 221.0
Percentage of Consolidated Net Income	55.00%	33.00%	54.00%	43.00%
Average Assets	$ 80,584.0	$ 75,696.5	$ 79,201.4	$ 75,534.7
Wealth Management
Segment Reporting Information [Line Items]
Trust, Investment and Other Servicing Fees	361.1	330.3	706.4	645.1
Foreign Exchange Trading Income	0.8	1.6	1.7	6.1
Other Noninterest Income	26.7	26.7	52.2	53.5
Net Interest Income	181.8	160.2	358.8	318.7
Revenue	570.4	518.8	1,119.1	1,023.4
Provision for Credit Losses	(4.3)	(2.2)	(5.6)	3.0
Noninterest Expense	350.9	330.3	697.2	657.2
Income before Income Taxes	223.8	190.7	427.5	363.2
Provision for Income Taxes	84.3	71.9	161.1	136.8
Net Income	$ 139.5	$ 118.8	$ 266.4	$ 226.4
Percentage of Consolidated Net Income	52.00%	45.00%	49.00%	45.00%
Average Assets	$ 26,823.5	$ 26,736.6	$ 26,743.1	$ 26,487.2
Treasury and Other
Segment Reporting Information [Line Items]
Trust, Investment and Other Servicing Fees	0.0	0.0	0.0	0.0
Foreign Exchange Trading Income	(1.5)	0.6	(3.4)	4.9
Other Noninterest Income	10.5	122.8	15.4	123.9
Net Interest Income	(7.4)	5.2	11.5	22.3
Revenue	1.6	128.6	23.5	151.1
Provision for Credit Losses	0.0	0.0	0.0	0.0
Noninterest Expense	40.9	37.9	78.3	64.5
Income before Income Taxes	(39.3)	90.7	(54.8)	86.6
Provision for Income Taxes	(20.2)	32.7	(40.2)	25.6
Net Income	$ (19.1)	$ 58.0	$ (14.6)	$ 61.0
Percentage of Consolidated Net Income	(7.00%)	22.00%	(3.00%)	12.00%
Average Assets	$ 10,993.2	$ 12,480.7	$ 11,499.3	$ 12,143.5