Related Party Transactions (Details) - ATC [Member] - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Related party transaction [Line Items]
Related party expenses	$ 28.2	$ 26.8	$ 27.7
Due from Related Parties	$ 0.2	$ 0.1	$ 0.2