Investment in Unconsolidated Affiliates Summarized Income Statement of Equity Method Investment (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Schedule of Equity Method Investments [Line Items]
Operating revenues	$ 590.0	$ 827.0	$ 1,206.0	$ 1,828.0
Cost of sales	277.0	478.0	569.0	1,111.0
Operating income	93.0	139.0	197.0	301.0
Net income	$ 77.0	$ 120.0	$ 168.0	$ 269.0