Equity Method Investments - Schedule of Equity Investments in Affiliates Balance Affected (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Schedule of Equity Method Investments [Line Items]
Distributions Received	$ 43.9	$ 26.3
Income from equity investments	38.7	23.2
Purchase price adjustment	0.4	0.0
Bengal
Schedule of Equity Method Investments [Line Items]
Distributions Received	4.7	6.3
Income from equity investments	5.3	5.4
Purchase price adjustment	0.0
Odyssey
Schedule of Equity Method Investments [Line Items]
Distributions Received	4.2
Income from equity investments	4.3
Purchase price adjustment	0.0
Mars
Schedule of Equity Method Investments [Line Items]
Distributions Received	23.3	9.9
Income from equity investments	21.5	10.9
Purchase price adjustment	0.0
Poseidon
Schedule of Equity Method Investments [Line Items]
Distributions Received	10.1	10.1
Income from equity investments	6.8	$ 6.9
Purchase price adjustment	0.0
Proteus
Schedule of Equity Method Investments [Line Items]
Distributions Received	0.9
Income from equity investments	0.4
Purchase price adjustment	0.3
Endymion
Schedule of Equity Method Investments [Line Items]
Distributions Received	0.7
Income from equity investments	0.4
Purchase price adjustment	$ 0.1