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		171,810			162,063		9,747	188,199			178,452		9,747
Other comprehensive income (loss)		72				72		(169)				(169)
Dividends on common stock ($1.48 per share)		(165,626)			(165,626)
Issuance of common stock (in shares)			201,699
Issuance of common stock		13,969	$ 13,969
Purchase of treasury stock (in shares)	[1]			(75,791)
Purchase of treasury stock	[1]	(6,882)		$ (6,882)
Reissuance of treasury stock for stock-based compensation and other (in shares)				75,707
Reissuance of treasury stock for stock-based compensation and other		6,567		$ 6,567	0
Capital activities by noncontrolling interests		(11,372)			0		(11,372)	(11,372)					(11,372)
Ending balance (in shares) at Jun. 30, 2019			(112,361,595)	(58,219)					(71,264,947)
Balance at end 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
Beginning balance (in shares) at Mar. 31, 2019			(112,340,322)	(63,271)					(71,264,947)
Balance at beginning of period at Mar. 31, 2019		5,381,725	$ 2,644,063	$ (5,586)	2,659,086	(46,501)	130,663	5,821,026	$ 178,162	2,721,696	2,816,532	(26,027)	130,663
Increase (Decrease) in Shareholders' Equity
Net Income		149,019			144,145		4,874	155,050			150,176		4,874
Other comprehensive income (loss)		(1,135)				(1,135)		(1,249)				(1,249)
Dividends on common stock ($1.48 per share)		(165,611)			(165,611)			(165,598)			(165,598)
Issuance of common stock (in shares)			21,273
Issuance of common stock		4,171	$ 4,171
Reissuance of treasury stock for stock-based compensation and other (in shares)				5,052
Reissuance of treasury stock for stock-based compensation and other		446		$ 446	0
Capital activities by noncontrolling interests		(11,372)			0		(11,372)	(11,372)					(11,372)
Ending balance (in shares) at Jun. 30, 2019			(112,361,595)	(58,219)					(71,264,947)
Balance at end 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
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		233,325			223,578		9,747	242,210			232,463		9,747
Other comprehensive income (loss)		(779)				(779)		497				497
Dividends on common stock ($1.48 per share)		(176,079)			(176,079)			(176,000)			(176,000)
Issuance of common stock (in shares)			50,998
Issuance of common stock		5,957	$ 5,957
Purchase of treasury stock (in shares)				(33,070)
Purchase of treasury stock		(3,010)		$ (3,010)
Reissuance of treasury stock for stock-based compensation and other (in shares)				100,633
Reissuance of treasury stock for stock-based compensation and other		9,247		$ 9,247	0
Other								(1)			(1)		0
Capital activities by noncontrolling interests		$ (11,372)			0		(11,372)						(11,372)
Ending balance (in shares) at Jun. 30, 2020		(112,591,124)	(112,591,124)	(35,983)					(71,264,947)
Balance at end 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
Beginning balance (in shares) at Mar. 31, 2020			(112,563,610)	(72,302)					(71,264,947)
Balance at beginning of period at Mar. 31, 2020		5,596,832	$ 2,664,387	$ (7,000)	2,867,610	(55,579)	127,414	6,040,344	$ 178,162	2,721,696	3,047,269	(34,197)	127,414
Increase (Decrease) in Shareholders' Equity
Net Income		198,459			193,585		4,874	201,992			197,118		4,874
Other comprehensive income (loss)		(2,296)				(2,296)		(828)				(828)
Dividends on common stock		(176,086)			(176,086)
Dividends on common stock ($1.48 per share)								(176,000)			(176,000)
Issuance of common stock (in shares)			27,514
Issuance of common stock		1,131	$ 1,131
Purchase of treasury stock (in shares)	[1]			(12,346)
Purchase of treasury stock	[1]	(924)		$ (924)
Reissuance of treasury stock for stock-based compensation and other (in shares)				48,665
Reissuance of treasury stock for stock-based compensation and other		4,734		$ 4,734	0
Other		(1)					(1)	1			2		(1)
Capital activities by noncontrolling interests		$ (11,372)			0		(11,372)	(11,372)					(11,372)
Ending balance (in shares) at Jun. 30, 2020		(112,591,124)	(112,591,124)	(35,983)					(71,264,947)
Balance at end 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

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