SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Schedule of Cumulative Effect of Changes made to Balance Sheet for the Adoption of Topic 606 (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Jan. 01, 2018	Dec. 31, 2017
Assets
Property, plant and equipment, net	$ 1,911,630	$ 1,828,252	$ 1,795,129
Liabilities
Deferred revenue	11,152	10,088	4,000
Deferred revenue, noncurrent	39,624	35,528	12,707
Partners' Capital	939,293	1,088,644
Calculated under Revenue Guidance in Effect before Topic 606
Assets
Property, plant and equipment, net	1,874,388		1,795,129
Liabilities
Deferred revenue	4,071		4,000
Deferred revenue, noncurrent	10,065		12,707
Partners' Capital	923,889		$ 1,084,430
Accounting Standard Update 2014-09 | Adjustments Due to Topic 606
Assets
Property, plant and equipment, net	37,242	33,123
Liabilities
Deferred revenue	7,081	6,088
Deferred revenue, noncurrent	29,559	22,821
Partners' Capital	$ 15,404	$ 4,214