Quarterly financial data (unaudited)

12 Months Ended

Dec. 31, 2020

Quarterly Financial Data [Abstract]

Quarterly financial data (unaudited)

Quarterly financial data (unaudited):

Summarized quarterly financial information for 2020 and 2019 is as follows:

	First Quarter		Second Quarter		Third Quarter		Fourth Quarter
	(dollars in thousands)
2020
Operating revenues	$	341,674	$	330,944	$	366,239	$	338,761
Operating margin	62,515		65,532		47,862		41,800
Net margin	23,204		26,162		8,471		(1,942)
2019
Operating revenues	$	356,600	$	358,860	$	382,623	$	332,209
Operating margin	66,032		51,712		59,209		40,256
Net margin	23,596		9,383		18,286		3,196

The negative net margins in the fourth quarter of 2020 were due to reductions to revenue requirements in order to achieve, but not exceed, the targeted margins for interest ratio of 1.14.