Investments in Joint Ventures - Schedule of Results of Operations of the Joint Ventures (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Operating Revenue and Expenses
Revenues	$ 211.9	$ 155.1
Expenses	103.9	83.5
Excess of revenues over expenses	$ 108.0	$ 71.6