EARNINGS PER UNIT (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Net income	$ 4,036	$ 8,767	$ 10,409	$ 22,630
Less: net income attributable to SMP Holdings	0	699	2,828	2,082
Net income attributable to SMLP	4,036	8,068	7,581	20,548
Less: net income attributable to general partner, including IDRs	801	161	1,232	411
Net income attributable to limited partners	3,235	7,907	6,349	20,137
Common units
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Net income attributable to limited partners	1,891	4,012	4,398	10,127
Weighted-average units outstanding - basic	34,422,273	25,172,087	32,179,431	24,790,158
Less: effect of non-vested phantom units and non-vested restricted units (in units)	196,233	109,017	180,591	80,875
Weighted-average units outstanding - diluted	34,618,506	25,281,104	32,360,022	24,871,033
Earnings per limited partner unit
Basic (in dollars per share)	$ 0.05	$ 0.16	$ 0.14	$ 0.41
Diluted (in dollars per share)	$ 0.05	$ 0.16	$ 0.14	$ 0.41
Subordinated Units
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Net income attributable to limited partners	$ 1,344	$ 3,895	$ 1,951	$ 10,010
Weighted-average units outstanding - basic	24,409,850	24,409,850	24,409,850	24,409,850
Weighted-average units outstanding - diluted	24,409,850	24,409,850	24,409,850	24,409,850
Earnings per limited partner unit
Basic (in dollars per share)	$ 0.05	$ 0.16	$ 0.08	$ 0.41
Diluted (in dollars per share)	$ 0.05	$ 0.16	$ 0.08	$ 0.41