Equity-Based Compensation Plans (Expense Related to Equity-Based Compensation Plans) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Expense related to equity-based compensation plan	$ (985)	$ 1,919	$ 1,971
Cost of goods and services sold | Onshore facilities and transportation
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Expense related to equity-based compensation plan	(209)	250	140
Cost of goods and services sold | Marine transportation
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Expense related to equity-based compensation plan	(51)	173	183
Cost of goods and services sold | Sodium minerals and sulfur services
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Expense related to equity-based compensation plan	(115)	140	112
Cost of goods and services sold | Offshore pipeline transportation
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Expense related to equity-based compensation plan	(277)	269	297
General and administrative expenses
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Expense related to equity-based compensation plan	$ (333)	$ 1,087	$ 1,239