Reporting Segments (Results of Reporting Segments) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Segment Reporting Information [Line Items]
Trust, Investment and Other Servicing Fees	$ 808.2	$ 748.2
Foreign Exchange Trading Income	48.1	60.5
Other Noninterest Income	74.6	73.5
Net Interest Income	362.4	314.0
Revenue	1,293.3	1,196.2
Provision for Credit Losses	(1.0)	2.0
Noninterest Expense	894.5	828.8
Income before Income Taxes	399.8	365.4
Provision for Income Taxes	123.7	120.0
Net Income	$ 276.1	$ 245.4
Percentage of Consolidated Net Income	100.00%	100.00%
Average Assets	$ 116,476.4	$ 113,417.1
FTE adjustments	8.9	6.2
Corporate & Institutional Services
Segment Reporting Information [Line Items]
Trust, Investment and Other Servicing Fees	462.9	433.4
Foreign Exchange Trading Income	49.1	51.7
Other Noninterest Income	44.2	45.6
Net Interest Income	166.5	138.4
Revenue	722.7	669.1
Provision for Credit Losses	0.3	(3.2)
Noninterest Expense	510.8	475.3
Income before Income Taxes	211.6	197.0
Provision for Income Taxes	66.9	62.2
Net Income	$ 144.7	$ 134.8
Percentage of Consolidated Net Income	52.00%	55.00%
Average Assets	$ 77,803.5	$ 75,372.9
Wealth Management
Segment Reporting Information [Line Items]
Trust, Investment and Other Servicing Fees	345.3	314.8
Foreign Exchange Trading Income	0.9	4.5
Other Noninterest Income	25.5	26.8
Net Interest Income	177.0	158.5
Revenue	548.7	504.6
Provision for Credit Losses	(1.3)	5.2
Noninterest Expense	346.3	326.9
Income before Income Taxes	203.7	172.5
Provision for Income Taxes	76.8	64.9
Net Income	$ 126.9	$ 107.6
Percentage of Consolidated Net Income	46.00%	44.00%
Average Assets	$ 26,661.8	$ 26,237.8
Treasury and Other
Segment Reporting Information [Line Items]
Trust, Investment and Other Servicing Fees	0.0	0.0
Foreign Exchange Trading Income	(1.9)	4.3
Other Noninterest Income	4.9	1.1
Net Interest Income	18.9	17.1
Revenue	21.9	22.5
Provision for Credit Losses	0.0	0.0
Noninterest Expense	37.4	26.6
Income before Income Taxes	(15.5)	(4.1)
Provision for Income Taxes	(20.0)	(7.1)
Net Income	$ 4.5	$ 3.0
Percentage of Consolidated Net Income	2.00%	1.00%
Average Assets	$ 12,011.1	$ 11,806.4