QUARTERLY FINANCIAL DATA (UNAUDITED) (Tables)

12 Months Ended

Dec. 31, 2017

QUARTERLY FINANCIAL DATA (UNAUDITED)

Schedule of Quarterly Financial Information

		First		Second			Third			Fourth
Statement of Operations Data		Quarter		Quarter			Quarter			Quarter			Total
2017
Operating revenues	$	338,429	$	338,901		$	396,511		$	314,752		$	1,388,593
Operating margins		51,018		36,970			74,946			20,763			183,697
Net margins attributable to the Association		23,526		4,791			40,798			(7,459)			61,656
2016
Operating revenues	$	323,462	$	320,622	(1)	$	378,352	(1)	$	318,660	(1)	$	1,341,096
Operating margins		46,379		37,003			52,199			11,425			147,006
Net margins attributable to the Association		17,533		2,537			17,739			(6,061)			31,748