Derivative Financial Instruments (Schedule of Interest Rate Derivatives) (Details) - USD ($)	Dec. 31, 2016	Dec. 31, 2015
HBB | Interest Rate Swaps
Derivative [Line Items]
Notional Amount	$ 20,000,000	$ 20,000,000
Average Fixed Rate	1.40%	1.40%
HBB | Delayed Start Interest Rate Swaps, Effective January 2024
Derivative [Line Items]
Notional Amount	$ 15,000,000	$ 0
Average Fixed Rate	1.60%	0.00%
HBB | Delayed Start Interest Rate Swaps, Effective January 2020
Derivative [Line Items]
Notional Amount	$ 10,000,000	$ 0
Average Fixed Rate	1.70%	0.00%
NACoal | Interest Rate Swaps
Derivative [Line Items]
Notional Amount	$ 80,000,000	$ 100,000,000
Average Fixed Rate	1.40%	1.40%