Borrowings (Schedule of Structured Financings and Pledged Assets) (Details) - USD ($) $ in Millions	Jun. 30, 2017	Dec. 31, 2016
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Secured Borrowing	$ 1,680.8	$ 1,925.7
Pledged Assets	4,037.6	4,148.3
TRS [Member]
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Secured Borrowing	511.3
Pledged Assets	827.2
Commercial Banking [Member]
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Secured Borrowing	1,642.2	1,809.9
Pledged Assets	3,999.0	3,935.7
Commercial Banking [Member] | Business Capital [Member]
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Secured Borrowing	830.1	949.8
Pledged Assets	2,704.4	2,608.0
Commercial Banking [Member] | Rail [Member]
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Secured Borrowing	812.1	860.1
Pledged Assets	1,294.6	1,327.5
Commercial Banking [Member] | Commercial Finance [Member]
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Secured Borrowing	0.0	0.0
Pledged Assets	0.0	0.2
Non-Strategic Portfolios [Member]
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Secured Borrowing	38.6	115.8
Pledged Assets	$ 38.6	$ 212.6