Reporting Segments (Results of Reporting Segments) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Segment Reporting Information [Line Items]
Trust, Investment and Other Servicing Fees	$ 788.3	$ 749.1	$ 2,313.7	$ 2,233.4
Foreign Exchange Trading Income	53.6	62.9	178.5	209.3
Other Noninterest Income	68.7	74.6	317.6	322.5
Net Interest Income	310.1	275.0	930.7	799.4
Revenue	1,220.7	1,161.6	3,740.5	3,564.6
Provision for Credit Losses	(3.0)	(10.0)	(4.0)	(24.5)
Noninterest Expense	843.0	812.3	2,596.8	2,455.8
Income before Income Taxes	380.7	359.3	1,147.7	1,133.3
Provision for Income Taxes	123.1	124.7	381.7	398.8
Net Income	$ 257.6	$ 234.6	$ 766.0	$ 734.5
Percentage of Consolidated Net Income	100.00%	100.00%	100.00%	100.00%
Average Assets	$ 116,382.5	$ 109,924.1	$ 114,909.9	$ 109,718.3
FTE adjustments	7.0	6.1	20.1	18.7
Corporate & Institutional Services
Segment Reporting Information [Line Items]
Trust, Investment and Other Servicing Fees	450.8	429.7	1,331.1	1,269.0
Foreign Exchange Trading Income	55.2	60.0	169.1	199.3
Other Noninterest Income	41.5	45.9	113.0	131.0
Net Interest Income	138.2	108.6	417.8	297.3
Revenue	685.7	644.2	2,031.0	1,896.6
Provision for Credit Losses	4.0	(2.8)	0.0	(3.0)
Noninterest Expense	487.8	464.6	1,519.9	1,387.7
Income before Income Taxes	193.9	182.4	511.1	511.9
Provision for Income Taxes	61.8	58.3	158.0	160.9
Net Income	$ 132.1	$ 124.1	$ 353.1	$ 351.0
Percentage of Consolidated Net Income	51.00%	53.00%	46.00%	48.00%
Average Assets	$ 75,696.5	$ 74,222.5	$ 75,589.0	$ 73,089.3
Wealth Management
Segment Reporting Information [Line Items]
Trust, Investment and Other Servicing Fees	337.5	319.4	982.6	964.4
Foreign Exchange Trading Income	0.9	2.9	7.0	10.0
Other Noninterest Income	26.3	28.3	79.8	83.9
Net Interest Income	164.1	142.5	482.8	421.8
Revenue	528.8	493.1	1,552.2	1,480.1
Provision for Credit Losses	(7.0)	(7.2)	(4.0)	(21.5)
Noninterest Expense	318.0	316.3	975.2	960.9
Income before Income Taxes	217.8	184.0	581.0	540.7
Provision for Income Taxes	82.3	69.0	219.1	203.2
Net Income	$ 135.5	$ 115.0	$ 361.9	$ 337.5
Percentage of Consolidated Net Income	53.00%	49.00%	47.00%	46.00%
Average Assets	$ 26,601.7	$ 25,201.2	$ 26,525.6	$ 24,732.4
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	(2.5)	0.0	2.4	0.0
Other Noninterest Income	0.9	0.4	124.8	107.6
Net Interest Income	7.8	23.9	30.1	80.3
Revenue	6.2	24.3	157.3	187.9
Provision for Credit Losses	0.0	0.0	0.0	0.0
Noninterest Expense	37.2	31.4	101.7	107.2
Income before Income Taxes	(31.0)	(7.1)	55.6	80.7
Provision for Income Taxes	(21.0)	(2.6)	4.6	34.7
Net Income	$ (10.0)	$ (4.5)	$ 51.0	$ 46.0
Percentage of Consolidated Net Income	(4.00%)	(2.00%)	7.00%	6.00%
Average Assets	$ 14,084.3	$ 10,500.4	$ 12,795.3	$ 11,896.6