Reporting Segments (Results of Reporting Segments) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Segment Reporting Information [Line Items]
Trust, Investment and Other Servicing Fees	$ 777.2	$ 756.8	$ 1,525.4	$ 1,484.3
Foreign Exchange Trading Income	64.4	74.8	124.9	146.4
Other Noninterest Income	175.4	173.1	248.9	247.9
Net Interest Income	306.6	257.6	620.6	524.4
Revenue	1,323.6	1,262.3	2,519.8	2,403.0
Provision for Credit Losses	(3.0)	(10.0)	(1.0)	(14.5)
Noninterest Expense	925.0	854.5	1,753.8	1,643.5
Income before Income Taxes	401.6	417.8	767.0	774.0
Provision for Income Taxes	140.9	148.6	264.5	274.1
Net Income	$ 260.7	$ 269.2	$ 502.5	$ 499.9
Percentage of Consolidated Net Income	100.00%	100.00%	100.00%	100.00%
Average Assets	$ 114,913.8	$ 111,691.1	$ 114,165.4	$ 109,613.7
FTE adjustments	6.9	6.4	13.1	12.6
Corporate & Institutional Services
Segment Reporting Information [Line Items]
Trust, Investment and Other Servicing Fees	446.9	432.0	880.3	839.3
Foreign Exchange Trading Income	62.2	71.8	113.9	139.3
Other Noninterest Income	25.9	43.2	71.5	85.1
Net Interest Income	141.2	92.7	279.6	188.7
Revenue	676.2	639.7	1,345.3	1,252.4
Provision for Credit Losses	(0.8)	2.0	(4.0)	(0.2)
Noninterest Expense	556.8	488.2	1,032.1	923.1
Income before Income Taxes	120.2	149.5	317.2	329.5
Provision for Income Taxes	34.0	45.3	96.2	102.6
Net Income	$ 86.2	$ 104.2	$ 221.0	$ 226.9
Percentage of Consolidated Net Income	33.00%	39.00%	44.00%	45.00%
Average Assets	$ 75,696.5	$ 75,765.9	$ 75,534.7	$ 72,513.3
Wealth Management
Segment Reporting Information [Line Items]
Trust, Investment and Other Servicing Fees	330.3	324.8	645.1	645.0
Foreign Exchange Trading Income	1.6	3.0	6.1	7.1
Other Noninterest Income	26.7	26.8	53.5	55.6
Net Interest Income	160.2	141.0	318.7	279.3
Revenue	518.8	495.6	1,023.4	987.0
Provision for Credit Losses	(2.2)	(12.0)	3.0	(14.3)
Noninterest Expense	330.3	322.7	657.2	644.6
Income before Income Taxes	190.7	184.9	363.2	356.7
Provision for Income Taxes	71.9	69.6	136.8	134.2
Net Income	$ 118.8	$ 115.3	$ 226.4	$ 222.5
Percentage of Consolidated Net Income	46.00%	43.00%	45.00%	45.00%
Average Assets	$ 26,736.6	$ 24,850.4	$ 26,487.2	$ 24,513.4
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	0.6	0.0	4.9	0.0
Other Noninterest Income	122.8	103.1	123.9	107.2
Net Interest Income	5.2	23.9	22.3	56.4
Revenue	128.6	127.0	151.1	163.6
Provision for Credit Losses	0.0	0.0	0.0	0.0
Noninterest Expense	37.9	43.6	64.5	75.8
Income before Income Taxes	90.7	83.4	86.6	87.8
Provision for Income Taxes	35.0	33.7	31.5	37.3
Net Income	$ 55.7	$ 49.7	$ 55.1	$ 50.5
Percentage of Consolidated Net Income	21.00%	18.00%	11.00%	10.00%
Average Assets	$ 12,480.7	$ 11,074.8	$ 12,143.5	$ 12,587.0