Loans (Schedule of Finance Receivables by Product) (Details) - USD ($) $ in Millions	Jun. 30, 2017	Dec. 31, 2016
Loans and Leases Receivable Disclosure [Line Items]
Total loans	$ 29,031.7	$ 29,535.9
Finance receivables held for sale	305.4	635.8
Finance receivables and held for sale receivables	29,337.1	30,171.7
Commercial Banking [Member]
Loans and Leases Receivable Disclosure [Line Items]
Total loans	22,722.9	22,970.7
Commercial Banking [Member] | Loans Receivable [Member]
Loans and Leases Receivable Disclosure [Line Items]
Total loans	19,902.3	20,117.8
Commercial Banking [Member] | Financing Receivable [Member]
Loans and Leases Receivable Disclosure [Line Items]
Total loans	2,820.6	2,852.9
Consumer Banking [Member]
Loans and Leases Receivable Disclosure [Line Items]
Total loans	$ 6,308.8	$ 6,565.2