Disposals and Impairments - Other Disposals (Details) $ in Millions	1 Months Ended		3 Months Ended	12 Months Ended
	Mar. 31, 2014 USD ($)	Feb. 28, 2014 USD ($)	Mar. 31, 2016 USD ($)	Mar. 31, 2016 USD ($) project	Mar. 31, 2015 USD ($)	Mar. 31, 2014 USD ($)
Disposals and Impairments
Number of canceled projects | project				2
Inventory write-down				$ 13.3	$ 16.8
Gavilon Energy | Natural Gas Storage and Transportation Contracts
Disposals and Impairments
Payments for assignment of contracts	$ 44.8
Assumed liabilities	50.8					$ 50.8
Amortization of contract liabilities through cost of sales	$ 6.0
Gavilon Energy | Natural Gas Storage and Transportation Contracts | Corporate and other
Disposals and Impairments
Operating income						1.4
High Sierra
Disposals and Impairments
Loss (gain) on sale of business		$ (4.4)
Proceeds from sale of business		10.8
Gain on the sale of the business attributable to noncontrolling interest		$ 1.6
High Sierra | Corporate and other
Disposals and Impairments
Operating income						2.3
Operating segment
Disposals and Impairments
Inventory write-down			$ 64.7
Operating segment | Crude oil logistics
Disposals and Impairments
Write down of property, plant and equipment				2.4
Inventory write-down			$ 47.7
Operating segment | Liquids
Disposals and Impairments
Write down of property, plant and equipment						5.3
Operating segment | Water solutions
Disposals and Impairments
Write down of property, plant and equipment					3.1	$ 1.5
Operating segment | Refined products and renewables
Disposals and Impairments
Write down of property, plant and equipment				14.6
Loss on Disposal or Impairment of Assets, Net | Operating segment | Crude oil logistics
Disposals and Impairments
Loss on canceled projects				3.1
Losses on property, plant and equipment				1.4
Loss on Disposal or Impairment of Assets, Net | Operating segment | Liquids
Disposals and Impairments
Loss on sale of terminal					29.8
Proceeds from Maine to relocate terminal assets				3.0
Losses on property, plant and equipment					21.7
Loss on goodwill allocated to assets sold					8.1
Loss on Disposal or Impairment of Assets, Net | Operating segment | Water solutions
Disposals and Impairments
Losses on property, plant and equipment					2.2
Loss (gain) on sale of business					4.0
Loss on goodwill allocated to assets sold					$ 1.8
Loss on Disposal or Impairment of Assets, Net | Operating segment | Refined products and renewables
Disposals and Impairments
Losses on property, plant and equipment				1.8
Tank bottoms | Loss on Disposal or Impairment of Assets, Net | Operating segment | Refined products and renewables
Disposals and Impairments
Losses on property, plant and equipment				$ 1.3