Equity Method Investments - Schedule of Equity Investments in Affiliates Balance Affected (Details) - USD ($) $ in Millions	3 Months Ended			9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015		Sep. 30, 2016	Sep. 30, 2015
Schedule of Equity Method Investments [Line Items]
Distributions received	$ 24.7	$ 23.2		$ 82.5	$ 51.9
Income from equity investments	21.4	24.1	[1]	70.2	47.4	[1]
Mars
Schedule of Equity Method Investments [Line Items]
Distributions received	11.5	7.7		34.5	24.9
Income from equity investments	8.6	10.5		31.7	23.6
Amortization expense (income)	0.2	0.2		0.7	0.7
Bengal
Schedule of Equity Method Investments [Line Items]
Distributions received	2.7	5.1		16.1	16.6
Income from equity investments	5.2	5.6		15.9	15.8
Amortization expense (income)	(0.1)	(0.1)		(0.2)	(0.2)
Poseidon
Schedule of Equity Method Investments [Line Items]
Distributions received	10.5	10.4		31.9	10.4
Income from equity investments	7.6	8.0		22.6	8.0
Amortization expense (income)	$ 0.2	$ 0.2		$ 0.6	$ 0.2

[1] (1) The 2015 financial information has been retrospectively adjusted for the acquisition of the Shell Auger and Lockport Operations.