Income Taxes - Income Tax Expense (Details) - USD ($) $ in Thousands	3 Months Ended			9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018		Sep. 30, 2019	Sep. 30, 2018
Income Tax Disclosure [Abstract]
Income taxes	$ 237	$ 98	[1]	$ 1,572	$ 379	[1]

[1] Financial information for 2018 has been revised to include results attributable to MTI acquired from Martin Resource Management Corporation. See Note 1 – Nature of Operations and Basis of Presentation.