Reporting Segments (Results of Reporting Segments) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Segment Reporting Information [Line Items]
Trust, Investment and Other Servicing Fees	$ 748.2	$ 727.5
Foreign Exchange Trading Income	60.5	71.6
Other Noninterest Income	73.5	74.8
Net Interest Income	314.0	266.8
Revenue	1,196.2	1,140.7
Provision for Credit Losses	2.0	(4.5)
Noninterest Expense	828.8	789.0
Income before Income Taxes	365.4	356.2
Provision for Income Taxes	123.6	125.5
Net Income	$ 241.8	$ 230.7
Percentage of Consolidated Net Income	100.00%	100.00%
Average Assets	$ 113,417.1	$ 107,513.2
FTE adjustments	6.2	6.2
Corporate & Institutional Services
Segment Reporting Information [Line Items]
Trust, Investment and Other Servicing Fees	433.4	407.3
Foreign Exchange Trading Income	51.7	67.5
Other Noninterest Income	45.6	41.9
Net Interest Income	138.4	96.0
Revenue	669.1	612.7
Provision for Credit Losses	(3.2)	(2.2)
Noninterest Expense	475.3	434.9
Income before Income Taxes	197.0	180.0
Provision for Income Taxes	62.2	57.3
Net Income	$ 134.8	$ 122.7
Percentage of Consolidated Net Income	56.00%	53.00%
Average Assets	$ 75,372.9	$ 69,224.5
Wealth Management
Segment Reporting Information [Line Items]
Trust, Investment and Other Servicing Fees	314.8	320.2
Foreign Exchange Trading Income	4.5	4.1
Other Noninterest Income	26.8	28.8
Net Interest Income	158.5	138.3
Revenue	504.6	491.4
Provision for Credit Losses	5.2	(2.3)
Noninterest Expense	326.9	321.9
Income before Income Taxes	172.5	171.8
Provision for Income Taxes	64.9	64.6
Net Income	$ 107.6	$ 107.2
Percentage of Consolidated Net Income	44.00%	47.00%
Average Assets	$ 26,237.8	$ 24,233.7
Treasury and Other
Segment Reporting Information [Line Items]
Trust, Investment and Other Servicing Fees	0.0	0.0
Foreign Exchange Trading Income	4.3	0.0
Other Noninterest Income	1.1	4.1
Net Interest Income	17.1	32.5
Revenue	22.5	36.6
Provision for Credit Losses	0.0	0.0
Noninterest Expense	26.6	32.2
Income before Income Taxes	(4.1)	4.4
Provision for Income Taxes	(3.5)	3.6
Net Income	$ (0.6)	$ 0.8
Percentage of Consolidated Net Income	0.00%	0.00%
Average Assets	$ 11,806.4	$ 14,055.0