Variable Interest Entities (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2013 Variable Interest, Held by Entity [Member]		Dec. 31, 2012 Variable Interest, Held by Entity [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Qualitative or Quantitative Information, Type of Entity	one
Carrying amounts of assets and liabilities of the VIE
Operating assets, net of accumulated depreciation		$ 93.0	[1]	$ 98.4	[1]
Nonrecourse debt		$ 25.4		$ 35.1

[1] (1) All operating assets are pledged as collateral on the nonrecourse debt.