Loans (Finance And Held-For-Sale Loans - By Risk Rating) (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Financing Receivable, Recorded Investment [Line Items]
Total	$ 30,209.6	$ 30,171.7
Commercial Banking
Financing Receivable, Recorded Investment [Line Items]
Total	23,807.9	23,538.3
Commercial Banking | Pass
Financing Receivable, Recorded Investment [Line Items]
Total	21,055.6	20,222.1
Commercial Banking | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Total	1,065.5	1,327.6
Commercial Banking | Classified- accruing
Financing Receivable, Recorded Investment [Line Items]
Total	1,428.3	1,611.4
Commercial Banking | Classified- non-accrual
Financing Receivable, Recorded Investment [Line Items]
Total	200.6	261.2
Commercial Banking
Financing Receivable, Recorded Investment [Line Items]
Total	23,326.1	22,919.9
Commercial Banking | Commercial Finance
Financing Receivable, Recorded Investment [Line Items]
Total	10,052.3	10,275.5
Commercial Banking | Real Estate Finance
Financing Receivable, Recorded Investment [Line Items]
Total	5,590.2	5,566.6
Commercial Banking | Business Capital
Financing Receivable, Recorded Investment [Line Items]
Total	7,579.8	6,974.1
Commercial Banking | Rail
Financing Receivable, Recorded Investment [Line Items]
Total	103.8	103.7
Commercial Banking | Commercial Banking
Financing Receivable, Recorded Investment [Line Items]
Total	23,326.1	22,919.9
Commercial Banking | Commercial Banking | Pass
Financing Receivable, Recorded Investment [Line Items]
Total	20,641.4	19,703.5
Commercial Banking | Commercial Banking | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Total	1,052.0	1,282.4
Commercial Banking | Commercial Banking | Classified- accruing
Financing Receivable, Recorded Investment [Line Items]
Total	1,386.2	1,569.9
Commercial Banking | Commercial Banking | Classified- non-accrual
Financing Receivable, Recorded Investment [Line Items]
Total	190.8	250.9
Commercial Banking | Commercial Banking | Commercial Finance
Financing Receivable, Recorded Investment [Line Items]
Total	10,052.3	10,275.5
Commercial Banking | Commercial Banking | Commercial Finance | Pass
Financing Receivable, Recorded Investment [Line Items]
Total	8,284.1	8,184.7
Commercial Banking | Commercial Banking | Commercial Finance | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Total	640.9	677.6
Commercial Banking | Commercial Banking | Commercial Finance | Classified- accruing
Financing Receivable, Recorded Investment [Line Items]
Total	981.9	1,181.7
Commercial Banking | Commercial Banking | Commercial Finance | Classified- non-accrual
Financing Receivable, Recorded Investment [Line Items]
Total	134.8	188.8
Commercial Banking | Commercial Banking | Real Estate Finance
Financing Receivable, Recorded Investment [Line Items]
Total	5,590.2	5,566.6
Commercial Banking | Commercial Banking | Real Estate Finance | Pass
Financing Receivable, Recorded Investment [Line Items]
Total	5,228.1	5,191.4
Commercial Banking | Commercial Banking | Real Estate Finance | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Total	139.9	168.7
Commercial Banking | Commercial Banking | Real Estate Finance | Classified- accruing
Financing Receivable, Recorded Investment [Line Items]
Total	174.3	115.6
Commercial Banking | Commercial Banking | Real Estate Finance | Classified- non-accrual
Financing Receivable, Recorded Investment [Line Items]
Total	2.8	20.4
Commercial Banking | Commercial Banking | Business Capital
Financing Receivable, Recorded Investment [Line Items]
Total	7,579.8	6,974.1
Commercial Banking | Commercial Banking | Business Capital | Pass
Financing Receivable, Recorded Investment [Line Items]
Total	7,028.6	6,238.7
Commercial Banking | Commercial Banking | Business Capital | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Total	269.2	422.0
Commercial Banking | Commercial Banking | Business Capital | Classified- accruing
Financing Receivable, Recorded Investment [Line Items]
Total	228.8	271.7
Commercial Banking | Commercial Banking | Business Capital | Classified- non-accrual
Financing Receivable, Recorded Investment [Line Items]
Total	53.2	41.7
Commercial Banking | Commercial Banking | Rail
Financing Receivable, Recorded Investment [Line Items]
Total	103.8	103.7
Commercial Banking | Commercial Banking | Rail | Pass
Financing Receivable, Recorded Investment [Line Items]
Total	100.6	88.7
Commercial Banking | Commercial Banking | Rail | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Total	2.0	14.1
Commercial Banking | Commercial Banking | Rail | Classified- accruing
Financing Receivable, Recorded Investment [Line Items]
Total	1.2	0.9
Commercial Banking | Commercial Banking | Rail | Classified- non-accrual
Financing Receivable, Recorded Investment [Line Items]
Total	0.0	0.0
Consumer Banking
Financing Receivable, Recorded Investment [Line Items]
Total	6,820.2	7,041.8
Consumer Banking | Other Consumer Banking
Financing Receivable, Recorded Investment [Line Items]
Total	3,489.1	2,179.1
Consumer Banking | Commercial Banking
Financing Receivable, Recorded Investment [Line Items]
Total	418.5	408.4
Consumer Banking | Commercial Banking | Pass
Financing Receivable, Recorded Investment [Line Items]
Total	378.5	374.9
Consumer Banking | Commercial Banking | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Total	5.9	8.3
Consumer Banking | Commercial Banking | Classified- accruing
Financing Receivable, Recorded Investment [Line Items]
Total	31.9	22.4
Consumer Banking | Commercial Banking | Classified- non-accrual
Financing Receivable, Recorded Investment [Line Items]
Total	0.0	0.0
Consumer Banking | Commercial Banking | Other Consumer Banking
Financing Receivable, Recorded Investment [Line Items]
Total	418.5	408.4
Consumer Banking | Commercial Banking | Other Consumer Banking | Pass
Financing Receivable, Recorded Investment [Line Items]
Total	378.5	374.9
Consumer Banking | Commercial Banking | Other Consumer Banking | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Total	5.9	8.3
Consumer Banking | Commercial Banking | Other Consumer Banking | Classified- accruing
Financing Receivable, Recorded Investment [Line Items]
Total	31.9	22.4
Consumer Banking | Commercial Banking | Other Consumer Banking | Classified- non-accrual
Financing Receivable, Recorded Investment [Line Items]
Total	0.0	0.0
Consumer Banking | Commercial Banking | SBA Loans
Financing Receivable, Recorded Investment [Line Items]
Total		370.1
Consumer Banking | Commercial Banking | Private Banking Loans
Financing Receivable, Recorded Investment [Line Items]
Total		38.3
Non-Strategic Portfolios | Commercial Banking
Financing Receivable, Recorded Investment [Line Items]
Total	63.3	210.0
Non-Strategic Portfolios | Commercial Banking | Pass
Financing Receivable, Recorded Investment [Line Items]
Total	35.7	143.7
Non-Strategic Portfolios | Commercial Banking | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Total	7.6	36.9
Non-Strategic Portfolios | Commercial Banking | Classified- accruing
Financing Receivable, Recorded Investment [Line Items]
Total	10.2	19.1
Non-Strategic Portfolios | Commercial Banking | Classified- non-accrual
Financing Receivable, Recorded Investment [Line Items]
Total	9.8	10.3
PCI Loans
Financing Receivable, Recorded Investment [Line Items]
Total	1,961.4	2,349.8
PCI Loans | Commercial Banking
Financing Receivable, Recorded Investment [Line Items]
Total	57.9	116.0
PCI Loans | Commercial Banking
Financing Receivable, Recorded Investment [Line Items]
Total	55.7	113.2
PCI Loans | Commercial Banking | Commercial Finance
Financing Receivable, Recorded Investment [Line Items]
Total	10.6	42.7
PCI Loans | Commercial Banking | Real Estate Finance
Financing Receivable, Recorded Investment [Line Items]
Total	45.1	70.5
PCI Loans | Commercial Banking | Business Capital
Financing Receivable, Recorded Investment [Line Items]
Total	0.0	0.0
PCI Loans | Commercial Banking | Rail
Financing Receivable, Recorded Investment [Line Items]
Total	0.0	0.0
PCI Loans | Commercial Banking | Commercial Banking
Financing Receivable, Recorded Investment [Line Items]
Total	55.7	113.2
PCI Loans | Commercial Banking | Commercial Banking | Commercial Finance
Financing Receivable, Recorded Investment [Line Items]
Total	10.6	42.7
PCI Loans | Commercial Banking | Commercial Banking | Real Estate Finance
Financing Receivable, Recorded Investment [Line Items]
Total	45.1	70.5
PCI Loans | Commercial Banking | Commercial Banking | Business Capital
Financing Receivable, Recorded Investment [Line Items]
Total	0.0	0.0
PCI Loans | Commercial Banking | Commercial Banking | Rail
Financing Receivable, Recorded Investment [Line Items]
Total	0.0	0.0
PCI Loans | Consumer Banking
Financing Receivable, Recorded Investment [Line Items]
Total	1,905.7	2,236.6
PCI Loans | Consumer Banking | Other Consumer Banking
Financing Receivable, Recorded Investment [Line Items]
Total	2.2	2.8
PCI Loans | Consumer Banking | Commercial Banking
Financing Receivable, Recorded Investment [Line Items]
Total	2.2	2.8
PCI Loans | Consumer Banking | Commercial Banking | Other Consumer Banking
Financing Receivable, Recorded Investment [Line Items]
Total	2.2	2.8
PCI Loans | Non-Strategic Portfolios | Commercial Banking
Financing Receivable, Recorded Investment [Line Items]
Total	$ 0.0	$ 0.0