Loans (Finance and Held For Sale Receivables - Delinquency Status) (Details) - USD ($) $ in Millions	Jun. 30, 2017	Dec. 31, 2016
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	$ 325.3	$ 339.5
Current	26,807.4	27,482.4
Total Finance Receivables	29,337.2	30,171.7
30 to 59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	141.8	204.0
60 to 89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	50.1	55.1
90 Days Or Greater [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	133.4	80.4
Non-Strategic Portfolios [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	14.4	11.1
Current	100.2	198.9
Total Finance Receivables	114.6	210.0
Non-Strategic Portfolios [Member] | 30 to 59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	3.9	3.0
Non-Strategic Portfolios [Member] | 60 to 89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	3.8	1.1
Non-Strategic Portfolios [Member] | 90 Days Or Greater [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	6.7	7.0
PCI Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Finance Receivables	2,204.5	2,349.8
Commercial Banking [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	247.5	250.2
Current	22,127.2	22,556.5
Total Finance Receivables	22,475.7	22,919.9
Commercial Banking [Member] | 30 to 59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	116.4	171.0
Commercial Banking [Member] | 60 to 89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	42.5	43.0
Commercial Banking [Member] | 90 Days Or Greater [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	88.6	36.2
Commercial Banking [Member] | PCI Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Finance Receivables	101.0	113.2
Consumer Banking [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	63.4	78.2
Current	4,580.0	4,727.0
Total Finance Receivables	6,746.9	7,041.8
Consumer Banking [Member] | 30 to 59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	21.5	30.0
Consumer Banking [Member] | 60 to 89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	3.8	11.0
Consumer Banking [Member] | 90 Days Or Greater [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	38.1	37.2
Consumer Banking [Member] | PCI Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Finance Receivables	2,103.5	2,236.6
Commercial Finance [Member] | Commercial Banking [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	100.0	39.0
Current	9,419.3	10,193.8
Total Finance Receivables	9,554.9	10,275.5
Commercial Finance [Member] | Commercial Banking [Member] | 30 to 59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	19.7	21.4
Commercial Finance [Member] | Commercial Banking [Member] | 60 to 89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	11.6
Commercial Finance [Member] | Commercial Banking [Member] | 90 Days Or Greater [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	68.7	17.6
Commercial Finance [Member] | Commercial Banking [Member] | PCI Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Finance Receivables	35.6	42.7
Real Estate Finance [Member] | Commercial Banking [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	3.3	0.1
Current	5,532.5	5,496.0
Total Finance Receivables	5,601.2	5,566.6
Real Estate Finance [Member] | Commercial Banking [Member] | 30 to 59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	0.0	0.1
Real Estate Finance [Member] | Commercial Banking [Member] | 90 Days Or Greater [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	3.3
Real Estate Finance [Member] | Commercial Banking [Member] | PCI Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Finance Receivables	65.4	70.5
Business Capital [Member] | Commercial Banking [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	142.0	202.3
Current	7,074.0	6,771.8
Total Finance Receivables	7,216.0	6,974.1
Business Capital [Member] | Commercial Banking [Member] | 30 to 59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	95.7	143.6
Business Capital [Member] | Commercial Banking [Member] | 60 to 89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	30.3	42.4
Business Capital [Member] | Commercial Banking [Member] | 90 Days Or Greater [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	16.0	16.3
Rail [Member] | Commercial Banking [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	2.2	8.8
Current	101.4	94.9
Total Finance Receivables	103.6	103.7
Rail [Member] | Commercial Banking [Member] | 30 to 59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	1.0	5.9
Rail [Member] | Commercial Banking [Member] | 60 to 89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	0.6	0.6
Rail [Member] | Commercial Banking [Member] | 90 Days Or Greater [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	0.6	2.3
Legacy Consumer Mortgages [Member] | Consumer Banking [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	61.8	65.3
Current	2,392.6	2,563.6
Total Finance Receivables	4,555.5	4,862.7
Legacy Consumer Mortgages [Member] | Consumer Banking [Member] | 30 to 59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	20.9	22.6
Legacy Consumer Mortgages [Member] | Consumer Banking [Member] | 60 to 89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	3.8	6.1
Legacy Consumer Mortgages [Member] | Consumer Banking [Member] | 90 Days Or Greater [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	37.1	36.6
Legacy Consumer Mortgages [Member] | Consumer Banking [Member] | PCI Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Finance Receivables	2,101.1	2,233.8
Other Consumer Banking [Member] | Consumer Banking [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	1.6	12.9
Current	2,187.4	2,163.4
Total Finance Receivables	2,191.4	2,179.1
Other Consumer Banking [Member] | Consumer Banking [Member] | 30 to 59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	0.6	7.4
Other Consumer Banking [Member] | Consumer Banking [Member] | 60 to 89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due		4.9
Other Consumer Banking [Member] | Consumer Banking [Member] | 90 Days Or Greater [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	1.0	0.6
Other Consumer Banking [Member] | Consumer Banking [Member] | PCI Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Finance Receivables	$ 2.4	$ 2.8