Transactions with Major Customers and Affiliates (Tables)

12 Months Ended

Dec. 31, 2015

Transactions with Major Customers and Affiliates [Abstract]

Schedule of revenue by major customers

During the periods presented, more than 10 percent of our operating revenues were generated from each of the following customers:

	Years Ended December 31,
	2015		2014		2013
	(Thousands of Dollars)
Puget Sound Energy, Inc.	$	118,384	$	113,398	$	110,111
Northwest Natural Gas Company	50,857		50,631		51,085
Cascade Natural Gas Corporation	48,363		(a)		(a)

(a) Under 10 percent in 2014 and 2013.