UNIT-BASED AND NONCASH COMPENSATION - Narrative (Details) - SMLP LTIP	1 Months Ended		9 Months Ended
	Jun. 30, 2020 Director shares	Mar. 31, 2020 Director $ / shares shares	Sep. 30, 2020 shares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Units remaining available			6,300,000
Phantom Units
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Granted units (in shares)		3,811,301
Grant date fair value (in dollars per share) | $ / shares		$ 0.55
Vesting period		3 years
Issued units (in shares)	187,500	549,450
No. of directors | Director	3	3
Units vested (in shares)			800,000
Number of authorized common units increased		15,000,000
Common units extended term		10 years