Related Party Transactions - Omnibus Agreement (Details) - Omnibus Agreement - Martin Resource Management - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Related Party Transaction
Non-compete restriction threshold	$ 5,000,000		$ 5,000,000
Non-compete restriction ownership option opportunity threshold minimum	5,000,000		5,000,000
Non-compete restriction ownership option opportunity threshold minimum with equity limitation	$ 5,000,000		$ 5,000,000
Equity limitation on ownership restriction percentage	20.00%		20.00%
Approved annual reimbursements for indirect expenses					$ 16,410,000
Indirect expenses reimbursed	$ 4,103,000	$ 4,164,000	$ 12,364,000	$ 12,492,000