Equity Method Investments - Summary of Income Statement Data for Equity Method Investments (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Mars
Schedule of Equity Method Investments [Line Items]
Total revenues	$ 57.3	$ 44.9
Total operating expenses	18.5	17.6
Operating income	38.8	27.3
Net income	38.8	27.4
Bengal
Schedule of Equity Method Investments [Line Items]
Total revenues	17.4	16.3
Total operating expenses	6.4	6.1
Operating income	11.0	10.2
Net income	11.0	$ 10.2
Poseidon
Schedule of Equity Method Investments [Line Items]
Total revenues	27.4
Total operating expenses	6.6
Operating income	20.8
Net income	$ 19.7