Equity - Distributions to Noncontrolling Interest (Details) - Zydeco - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	May 31, 2016	May 31, 2015	Nov. 03, 2014
Class of Stock [Line Items]
Distributions to noncontrolling interest	$ 20.3	$ 67.1	$ 32.0
Minority interest ownership percentage by noncontrolling owners	7.50%	37.50%		7.50%	37.50%	57.00%
Shell Pipeline Company L P
Class of Stock [Line Items]
Distributions paid			$ 25.2
Minority interest ownership percentage by noncontrolling owners			57.00%
Pre-offering distribution payable			$ 6.8