Equity and Distributions, Noncontrolling Interests (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Components of net income attributable to noncontrolling interests
Limited partners of Oiltanking other than EPO	$ 0.0	$ 0.0	$ 7.8
Joint venture partners	56.3	39.9	29.4
Total	56.3	39.9	37.2
Cash distributions paid to noncontrolling interests:
Limited partners of Oiltanking other than EPO	0.0	0.0	8.1
Joint venture partners	49.2	47.4	39.9
Total	49.2	47.4	48.0
Cash contributions from noncontrolling interests:
Joint venture partners	$ 0.4	$ 20.4	54.0
Oiltanking Partners L.P. [Member]
Noncontrolling Interest
Noncontrolling interests acquired			$ 1,400.0