Summary of Significant Accounting Policies - Summary of Net Purchase Cost Adjustment and Amortization of Equity Method Investment (Details) - USD ($) $ in Millions		1 Months Ended	2 Months Ended	12 Months Ended
		Jul. 31, 2015	Dec. 31, 2014	Dec. 31, 2015
Summary Of Significant Accounting Policies [Line Items]
Acquired on November 3, 2014			$ 5.9	$ 5.8
Amortization			0.1	1.1
Balance			5.8	15.4
July 2015 Acquisition				10.7
Mars
Summary Of Significant Accounting Policies [Line Items]
Acquired on November 3, 2014			12.2	12.1
Amortization			0.1	1.0
Balance			12.1	11.1
Bengal
Summary Of Significant Accounting Policies [Line Items]
Acquired on November 3, 2014	[1]		(6.3)	(6.3)
Amortization	[1]			(0.3)
Balance	[1]		$ (6.3)	(6.0)
Poseidon
Summary Of Significant Accounting Policies [Line Items]
Amortization	[2]			0.4
Balance	[2]			10.3
July 2015 Acquisition		$ 30.5		$ 10.7	[2]

[1] Our equity investment balance is recorded net of a deferred gain upon the formation of the joint venture in Bengal.

[2] We acquired an equity interest in Poseidon on July 1, 2015. For additional information regarding this transaction, see Note 3 - Acquisitions.