REVENUE FROM CONTRACTS WITH CUSTOMERS - Disaggregated (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Disaggregation of Revenue [Line Items]
Total revenue	$ 70,232	$ 66,573	$ 64,969	$ 61,268	$ 60,992	$ 57,752	$ 56,148	$ 57,405	$ 263,042	$ 232,297	$ 184,447
Firm commitments revenue
Disaggregation of Revenue [Line Items]
ASC 842/840 revenue									178,214	158,055
ASC 606 revenue									14,226	13,719
Total revenue									192,440	171,774
Ancillary revenue
Disaggregation of Revenue [Line Items]
ASC 842/840 revenue									4,448	2,378
ASC 606 revenue									44,062	42,079
Total revenue									48,510	44,457
Terminaling services fees
Disaggregation of Revenue [Line Items]
Total revenue									240,950	216,231
Pipeline transportation fees
Disaggregation of Revenue [Line Items]
ASC 842/840 revenue									3,457	3,295
Management fees
Disaggregation of Revenue [Line Items]
ASC 842/840 revenue									1,799	223
ASC 606 revenue									16,836	12,548
Total revenue									$ 18,635	$ 12,771