Variable Interest Entities (Details) - USD ($) $ in Millions		6 Months Ended
		Jun. 30, 2015	Dec. 31, 2014
Variable Interest Entity [Line Items]
Variable Interest Entity, Qualitative or Quantitative Information, Type of Entity		one
Variable Interest, Held by Entity [Member]
Carrying amounts of assets and liabilities of the VIE
Operating assets, net of accumulated depreciation	[1]	$ 85.6	$ 88.1
Nonrecourse debt		$ 11.5	$ 15.9

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