Borrowings (Schedule of Structured Financings and Pledged Assets) (Details) - USD ($) $ in Millions	Sep. 30, 2017	Dec. 31, 2016
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Secured Borrowing	$ 1,637.7	$ 1,925.7
Pledged Assets	4,472.5	4,148.3
Assets Held-For-Sale (AHFS) | NACCO Subsidiaries
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Secured borrowings	254.7
Pledged assets	423.3
Total Return Swap (TRS)
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Secured Borrowing	501.9
Pledged Assets	820.1
Commercial Banking
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Secured Borrowing	1,597.6	1,809.9
Pledged Assets	4,432.4	3,935.7
Commercial Banking | Business Capital
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Secured Borrowing	796.6	949.8
Pledged Assets	3,139.8	2,608.0
Commercial Banking | Rail
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Secured Borrowing	801.0	860.1
Pledged Assets	1,292.6	1,327.5
Commercial Banking | Commercial Finance
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
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Secured Borrowing	40.1	115.8
Pledged Assets	$ 40.1	$ 212.6