Reporting Segments (Results of Reporting Segments) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Segment Reporting Information [Line Items]
Segment Reporting Information, Fully Taxable-Equivalent Adjustment	$ 6.1	$ 6.9	$ 18.7	$ 22.4
Trust, Investment and Other Servicing Fees	749.1	718.2	2,233.4	2,104.6
Foreign Exchange Trading Income	62.9	46.4	209.3	149.4
Other Noninterest Income	74.6	65.0	322.5	205.5
Net Interest Income (FTE)	275.0	256.2	799.4	764.0
Revenue	1,161.6	1,085.8	3,564.6	3,223.5
Provision for Credit Losses	(10.0)	0.0	(24.5)	3.0
Noninterest Expense	812.3	774.7	2,455.8	2,353.7
Income before Income Taxes	359.3	311.1	1,133.3	866.8
Provision for Income Taxes	124.7	106.6	398.8	299.0
Net Income	$ 234.6	$ 204.5	$ 734.5	$ 567.8
Percentage of Consolidated Net Income	100.00%	100.00%	100.00%	100.00%
Average Assets	$ 109,924.1	$ 105,244.7	$ 109,718.3	$ 102,955.8
Corporate & Institutional Services
Segment Reporting Information [Line Items]
Trust, Investment and Other Servicing Fees	429.7	399.9	1,269.0	1,174.5
Foreign Exchange Trading Income	60.0	44.4	199.3	143.2
Other Noninterest Income	45.9	42.8	131.0	134.3
Net Interest Income (FTE)	108.6	78.4	297.3	228.8
Revenue	644.2	565.5	1,896.6	1,680.8
Provision for Credit Losses	(2.8)	0.9	(3.0)	4.5
Noninterest Expense	464.6	429.6	1,387.7	1,299.5
Income before Income Taxes	182.4	135.0	511.9	376.8
Provision for Income Taxes	58.3	42.4	160.9	113.3
Net Income	$ 124.1	$ 92.6	$ 351.0	$ 263.5
Percentage of Consolidated Net Income	53.00%	45.00%	48.00%	46.00%
Average Assets	$ 41,305.7	$ 59,907.1	$ 41,461.6	$ 59,061.3
Wealth Management
Segment Reporting Information [Line Items]
Trust, Investment and Other Servicing Fees	319.4	318.3	964.4	930.1
Foreign Exchange Trading Income	2.9	2.0	10.0	6.2
Other Noninterest Income	28.3	20.9	83.9	66.7
Net Interest Income (FTE)	142.5	131.2	421.8	398.8
Revenue	493.1	472.4	1,480.1	1,401.8
Provision for Credit Losses	(7.2)	(0.9)	(21.5)	(1.5)
Noninterest Expense	316.3	312.1	960.9	960.3
Income before Income Taxes	184.0	161.2	540.7	443.0
Provision for Income Taxes	69.0	60.7	203.2	166.9
Net Income	$ 115.0	$ 100.5	$ 337.5	$ 276.1
Percentage of Consolidated Net Income	49.00%	49.00%	46.00%	49.00%
Average Assets	$ 25,274.6	$ 26,061.8	$ 24,806.8	$ 23,613.4
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	0.0	0.0	0.0	0.0
Other Noninterest Income	0.4	1.3	107.6	4.5
Net Interest Income (FTE)	23.9	46.6	80.3	136.4
Revenue	24.3	47.9	187.9	140.9
Provision for Credit Losses	0.0	0.0	0.0	0.0
Noninterest Expense	31.4	33.0	107.2	93.9
Income before Income Taxes	(7.1)	14.9	80.7	47.0
Provision for Income Taxes	(2.6)	3.5	34.7	18.8
Net Income	$ (4.5)	$ 11.4	$ 46.0	$ 28.2
Percentage of Consolidated Net Income	(2.00%)	6.00%	6.00%	5.00%
Average Assets	$ 43,343.8	$ 19,275.8	$ 43,449.9	$ 20,281.1