Rate and Regulatory Matters (Tables)

12 Months Ended

Dec. 31, 2016

Regulated Operations [Abstract]

Schedule of regulatory assets

	(Thousands of Dollars)
	December 31,				Remaining
Regulatory Assets	2016		2015		Recovery Periods
Retirement Benefits	$	40,603	$	39,378	Various
Income Taxes		15,899		15,541	Various
Rate Cases, Tank Painting, and Other		4,392		3,633	2-10 years
Total	$	60,894	$	58,552