CONDENSED CONSOLIDATED STATEMENTS OF CHANGES IN EQUITY - USD ($) $ in Thousands		Total	Common Stock	Treasury Stock	Retained Earnings	Accumulated Other Comprehensive Income (Loss)	Noncontrolling Interests	APS	APS Common Stock	APS Additional Paid-In Capital	APS Retained Earnings	APS Accumulated Other Comprehensive Income (Loss)	APS Noncontrolling Interests
Beginning balance (in shares) at Dec. 31, 2019			112,540,126	103,546					71,264,947
Balance at beginning of period at Dec. 31, 2019		$ 5,553,188	$ 2,659,561	$ (9,427)	$ 2,837,610	$ (57,096)	$ 122,540	$ 5,998,803	$ 178,162	$ 2,721,696	$ 3,011,927	$ (35,522)	$ 122,540
Increase (Decrease) in Shareholders' Equity
Net income		584,570			569,950		14,620	597,446			582,826		14,620
Other comprehensive income (loss)		(395)				(395)		1,397				1,397
Dividends on common stock		(176,079)			(176,079)			(176,000)			(176,000)
Issuance of common stock (in shares)			83,497
Issuance of common stock		10,797	$ 10,797
Purchase of treasury stock (in shares)	[1]			(34,569)
Purchase of treasury stock	[1]	(3,119)		$ (3,119)
Reissuance of treasury stock for stock-based compensation and other (in shares)				104,398
Reissuance of treasury stock for stock-based compensation and other		9,580		$ 9,580
Capital activities by noncontrolling interests		(11,372)					(11,372)	(11,372)					(11,372)
Other		5			4		1	1					1
Ending balance (in shares) at Sep. 30, 2020			112,623,623	33,717					71,264,947
Balance at end of period at Sep. 30, 2020		5,967,175	$ 2,670,358	$ (2,966)	3,231,485	(57,491)	125,789	6,410,275	$ 178,162	2,721,696	3,418,753	(34,125)	125,789
Beginning balance (in shares) at Jun. 30, 2020			112,591,124	35,983					71,264,947
Balance at beginning of period at Jun. 30, 2020		5,610,477	$ 2,665,518	$ (3,190)	2,885,109	(57,875)	120,915	6,054,137	$ 178,162	2,721,696	3,068,389	(35,025)	120,915
Increase (Decrease) in Shareholders' Equity
Net income		351,245			346,372		4,873	355,236			350,363		4,873
Other comprehensive income (loss)		384				384		900				900
Dividends on common stock		1			1
Issuance of common stock (in shares)			32,499
Issuance of common stock		4,840	$ 4,840
Purchase of treasury stock (in shares)	[2]			(1,499)
Purchase of treasury stock	[2]	(109)		$ (109)
Reissuance of treasury stock for stock-based compensation and other (in shares)				3,765
Reissuance of treasury stock for stock-based compensation and other		333		$ 333
Other		4			3		1	2			1		1
Ending balance (in shares) at Sep. 30, 2020			112,623,623	33,717					71,264,947
Balance at end of period at Sep. 30, 2020		$ 5,967,175	$ 2,670,358	$ (2,966)	3,231,485	(57,491)	125,789	6,410,275	$ 178,162	2,721,696	3,418,753	(34,125)	125,789
Beginning balance (in shares) at Dec. 31, 2020		112,760,051	112,760,051	72,006					71,264,947
Balance at beginning of period at Dec. 31, 2020		$ 5,752,793	$ 2,677,482	$ (6,289)	3,025,106	(62,796)	119,290	6,345,185	$ 178,162	2,871,696	3,216,955	(40,918)	119,290
Increase (Decrease) in Shareholders' Equity
Net income		604,054			591,136		12,918	611,616			598,698		12,918
Other comprehensive income (loss)		3,130				3,130		2,086				2,086
Dividends on common stock		(187,165)			(187,165)			(187,000)			(187,000)
Issuance of common stock (in shares)			92,070
Issuance of common stock		21,070	$ 21,070
Purchase of treasury stock (in shares)	[1]			(17,437)
Purchase of treasury stock	[1]	(1,333)		$ (1,333)
Reissuance of treasury stock for stock-based compensation and other (in shares)				53,290
Reissuance of treasury stock for stock-based compensation and other		4,543		$ 4,543
Capital activities by noncontrolling interests		(10,628)					(10,628)	(10,628)					(10,628)
Other		$ 0			(1)		1	0			(1)		1
Ending balance (in shares) at Sep. 30, 2021		112,852,121	112,852,121	36,153					71,264,947
Balance at end of period at Sep. 30, 2021		$ 6,186,464	$ 2,698,552	$ (3,079)	3,429,076	(59,666)	121,581	6,761,259	$ 178,162	2,871,696	3,628,652	(38,832)	121,581
Beginning balance (in shares) at Jun. 30, 2021			112,819,703	36,153					71,264,947
Balance at beginning of period at Jun. 30, 2021		5,834,899	$ 2,692,015	$ (3,079)	3,089,266	(60,578)	117,275	6,412,290	$ 178,162	2,871,696	3,284,989	(39,832)	117,275
Increase (Decrease) in Shareholders' Equity
Net income		344,104			339,798		4,306	347,969			343,663		4,306
Other comprehensive income (loss)		912				912		1,000				1,000
Dividends on common stock		11			11
Issuance of common stock (in shares)			32,418
Issuance of common stock		6,537	$ 6,537
Other		$ 1			1
Ending balance (in shares) at Sep. 30, 2021		112,852,121	112,852,121	36,153					71,264,947
Balance at end of period at Sep. 30, 2021		$ 6,186,464	$ 2,698,552	$ (3,079)	$ 3,429,076	$ (59,666)	$ 121,581	$ 6,761,259	$ 178,162	$ 2,871,696	$ 3,628,652	$ (38,832)	$ 121,581

[1] Primarily represents shares of common stock withheld from certain stock awards for tax purposes.

[2] Primarily represents shares of common stock withheld from certain stock awards for tax purposes.