QUARTERLY FINANCIAL DATA (UNAUDITED) (Tables)

12 Months Ended

Dec. 31, 2016

Quarterly Financial Data [Abstract]

Schedule of Quarterly Financial Information

The following table summarizes quarterly financial data for the years ended December 31, 2016 and 2015:

	First Quarter		Second Quarter		Third Quarter		Fourth Quarter		Total
	(Thousands of Dollars, Except Per Unit Data)
2016:
Net income	$	16,676	$	15,073	$	17,320	$	5,999	$	55,068
Basic and diluted net income per unit	0.39		0.35		0.40		0.14		1.28
Cash distributions per unit	0.545		0.545		0.545		0.545		2.180
2015:
Net income	$	26,805	$	15,527	$	16,917	$	12,959	$	72,208
Basic and diluted net income per unit	0.62		0.37		0.39		0.30		1.68
Cash distributions per unit	0.545		0.545		0.545		0.545		2.180