NET INCOME PER COMMON SHARE (Tables)

12 Months Ended

Dec. 31, 2017

NET INCOME PER COMMON SHARE [Abstract]

Net Income Per Common Share

	Year ended December 31,
	2017		2016		2015
	(thousands of dollars)
Net income	$	18,009	$	19,428	$	18,598
Basic earnings per common share:
Weighted average shares outstanding		24,294		24,284		24,370
Per share amount (dollars)	$	0.74	$	0.80	$	0.76
Diluted earnings per common share:
Weighted average shares outstanding		25,129		24,982		25,181
Per share amount (dollars)	$	0.72	$	0.78	$	0.74

Weighted average shares-denominator   basic computation	24,294	24,284	24,370
Unvested restricted stock unit grant	367	310	141
Effect of dilutive stock options	468	388	670
Weighted average shares, as adjusted   denominator diluted computation	25,129	24,982	25,181