Derivative Financial Instruments (Interest Rate Derivatives) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Dec. 31, 2013	Mar. 31, 2013
Derivative [Line Items]
Derivative, Notional Amount	$ 11.0	$ 5.0	$ 8.6
HBB
Derivative [Line Items]
Derivative, Notional Amount	20.0	20.0	25.0
Average Fixed Rate	1.40%	1.40%	4.00%
Remaining Term	extending to January 2020
NACoal
Derivative [Line Items]
Derivative, Notional Amount	$ 100.0	$ 100.0
Average Fixed Rate	1.40%	1.40%
Remaining Term	extending to May 2018