Selected Quarterly Financial Data (Unaudited) (Tables)

12 Months Ended

Dec. 31, 2019

Quarterly Financial Information Disclosure [Abstract]

Schedule of quarterly financial information

Consolidated quarterly financial information for 2019 and 2018 is provided in the tables below (dollars in thousands, except per share amounts).  Weather conditions cause significant seasonal fluctuations in our revenues; therefore, results for interim periods do not necessarily represent results expected for the year.

	2019 Quarter Ended									2019
	March 31,		June 30,		September 30,		December 31,			Total
Operating revenues	$	740,530	$	869,501	$	1,190,787	$	670,391		$	3,471,209
Operations and maintenance	245,634		227,543		238,582		229,857			941,616
Operating income	60,084		196,589		403,290		11,997			671,960
Income taxes	2,418		17,080		53,266		(88,537		)	(15,773		)
Net income	22,791		149,019		317,149		68,854			557,813
Net income attributable to common shareholders	17,918		144,145		312,276		63,981			538,320
Earnings Per Share:
Net income attributable to common shareholders — Basic	$	0.16	$	1.28	$	2.78	$	0.57		$	4.79
Net income attributable to common shareholders — Diluted	0.16		1.28		2.77		0.57			4.77

	2018 Quarter Ended									2018
	March 31,			June 30,		September 30,		December 31,		Total
Operating revenues	$	692,714		$	974,123	$	1,268,034	$	756,376	$	3,691,247
Operations and maintenance	265,682			268,397		246,545		256,120		1,036,744
Operating income	31,334			242,162		433,307		66,884		773,687
Income taxes	(1,265		)	44,039		84,333		6,795		133,902
Net income	8,094			171,612		319,885		30,949		530,540
Net income attributable to common shareholders	3,221			166,738		315,012		26,076		511,047
Earnings Per Share:
Net income attributable to common shareholders — Basic	$	0.03		$	1.49	$	2.81	$	0.23	$	4.56
Net income attributable to common shareholders — Diluted	0.03			1.48		2.80		0.23		4.54

APS's quarterly financial information for 2019 and 2018 is as follows (dollars in thousands):

	2019 Quarter Ended								2019
	March 31,		June 30,		September 30,		December 31,		Total
Operating revenues	$	740,530	$	869,501	$	1,190,787	$	670,391	$	3,471,209
Operations and maintenance	240,375		224,143		235,440		226,758		926,716
Operating income	65,377		200,018		406,465		15,124		686,984
Net income attributable to common shareholder	28,276		150,176		318,870		67,949		565,271

	2018 Quarter Ended								2018
	March 31,		June 30,		September 30,		December 31,		Total
Operating revenues	$	692,006	$	971,963	$	1,267,997	$	756,376	$	3,688,342
Operations and maintenance	254,601		251,999		226,346		236,281		969,227
Operating income	37,878		251,590		453,547		86,753		829,768
Net income attributable to common shareholder	9,599		177,825		338,366		44,475		570,265