Quarterly financial data (unaudited)

12 Months Ended

Dec. 31, 2022

Quarterly Financial Data [Abstract]

Quarterly financial data (unaudited)

Quarterly financial data (unaudited):Summarized quarterly financial information for 2022 and 2021 is as follows:

	First Quarter		Second Quarter		Third Quarter		Fourth Quarter
	(dollars in thousands)
2022
Operating revenues	$	420,442	$	533,128	$	704,265	$	472,302
Operating margin	57,845		54,269		64,553		17,384
Net margin	21,980		18,167		32,097		(10,540)
2021
Operating revenues	$	376,331	$	358,127	$	460,822	$	409,583
Operating margin	64,573		53,035		46,025		30,748
Net margin	25,958		13,145		8,907		9,771