CONDENSED CONSOLIDATED STATEMENTS OF CHANGES IN EQUITY (Unaudited) - 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, 2018			112,159,896	58,135					71,264,947
Balance at beginning of period at Dec. 31, 2018		$ 5,348,705	$ 2,634,265	$ (4,825)	$ 2,641,183	$ (47,708)	$ 125,790	$ 5,786,797	$ 178,162	$ 2,721,696	$ 2,788,256	$ (27,107)	$ 125,790
Increase (Decrease) in Shareholders' Equity
Net Income		488,959			474,339		14,620	511,942			497,322		14,620
Other comprehensive income (loss)		1,170				1,170		804				804
Dividends on common stock		(165,631)			(165,631)
Issuance of common stock (in shares)			243,855
Issuance of common stock		20,165	$ 20,165
Purchase of treasury stock (in shares)	[1]			(75,894)
Purchase of treasury stock	[1]	(6,892)		$ (6,892)
Reissuance of treasury stock for stock-based compensation and other (in shares)				76,082
Reissuance of treasury stock for stock-based compensation and other		6,600		$ 6,600	0
Other								0			(1)		1
Capital activities by noncontrolling interests		(11,372)			0		(11,372)	(11,372)					(11,372)
Ending balance (in shares) at Sep. 30, 2019			112,403,751	57,947					71,264,947
Balance at end of period at Sep. 30, 2019		5,681,705	$ 2,654,430	$ (5,117)	2,949,891	(46,538)	129,039	6,122,571	$ 178,162	2,721,696	3,119,977	(26,303)	129,039
Beginning balance (in shares) at Jun. 30, 2019			112,361,595	58,219					71,264,947
Balance at beginning of period at Jun. 30, 2019		5,357,243	$ 2,648,234	$ (5,140)	2,637,620	(47,636)	124,165	5,797,857	$ 178,162	2,721,696	2,801,110	(27,276)	124,165
Increase (Decrease) in Shareholders' Equity
Net Income		317,149			312,276		4,873	323,743			318,870		4,873
Other comprehensive income (loss)		1,098				1,098		973				973
Dividends on common stock		(5)			(5)			(165,600)			(165,600)
Issuance of common stock (in shares)			42,156
Issuance of common stock		6,196	$ 6,196
Purchase of treasury stock (in shares)				(103)
Purchase of treasury stock		(10)		$ (10)
Reissuance of treasury stock for stock-based compensation and other (in shares)				375
Reissuance of treasury stock for stock-based compensation and other		33		$ 33	0
Other		1					1	(2)			(3)		1
Ending balance (in shares) at Sep. 30, 2019			112,403,751	57,947					71,264,947
Balance at end of period at Sep. 30, 2019		$ 5,681,705	$ 2,654,430	$ (5,117)	2,949,891	(46,538)	129,039	6,122,571	$ 178,162	2,721,696	3,119,977	(26,303)	129,039
Beginning balance (in shares) at Dec. 31, 2019		112,540,126	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)				(34,569)
Purchase of treasury stock		(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	0
Other		5			(4)		1	1			0		1
Capital activities by noncontrolling interests		$ (11,372)			0		(11,372)						(11,372)
Ending balance (in shares) at Sep. 30, 2020		112,623,623	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)	[1]			(1,499)
Purchase of treasury stock	[1]	(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	0
Other		$ 4					1	2			1		1
Capital activities by noncontrolling interests					3			(11,372)
Ending balance (in shares) at Sep. 30, 2020		112,623,623	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

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