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, 2017			(111,816,170)	(64,463)							(71,264,947)
Balance at beginning of period at Dec. 31, 2017		$ 5,135,730	$ 2,614,805	$ (5,624)	$ 2,442,511		$ (45,002)		$ 129,040	$ 5,385,869	$ 178,162	$ 2,571,696	$ 2,533,954		$ (26,983)		$ 129,040
Increase (Decrease) in Shareholders' Equity
Net income		179,706			169,959				9,747	197,170			187,423				9,747
Other comprehensive loss		(3,070)					(3,070)			(3,138)					(3,138)
Dividends on common stock		(155,620)			(155,620)					(155,599)			(155,599)
Issuance of common stock (in shares)			174,052
Issuance of common stock		9,867	$ 9,867
Purchase of treasury stock (in shares)	[1]			(81,177)
Purchase of treasury stock	[1]	(6,277)		$ (6,277)
Reissuance of treasury stock for stock-based compensation and other (in shares)				128,007
Reissuance of treasury stock for stock-based compensation and other		10,470		$ 10,470	0				0
Reclassification of income tax effects related to new tax reform		(8,552)			8,552	[2]	(8,552)	[2]					5,038	[3]	(5,038)	[3]
Capital activities by noncontrolling interests		(11,372)							(11,372)	(11,372)							(11,372)
Ending balance (in shares) at Jun. 30, 2018			(111,990,222)	(17,633)							(71,264,947)
Balance at end of period at Jun. 30, 2018		5,159,434	$ 2,624,672	$ (1,431)	2,465,402		(56,624)		127,415	5,412,930	$ 178,162	2,571,696	2,570,816		(35,159)		127,415
Beginning balance (in shares) at Mar. 31, 2018			(111,961,963)	(29,097)							(71,264,947)
Balance at beginning of period at Mar. 31, 2018		5,153,671	$ 2,620,261	$ (2,431)	2,454,268		(52,341)		133,914	5,401,512	$ 178,162	2,571,696	2,548,591		(30,851)		133,914
Increase (Decrease) in Shareholders' Equity
Net income		171,612			166,738				4,874	182,699			177,825				4,874
Other comprehensive loss		(4,283)					(4,283)			(4,308)					(4,308)
Other										(1)							(1)
Dividends on common stock		(155,604)			(155,604)					(155,600)			(155,600)
Issuance of common stock (in shares)			28,259
Issuance of common stock		4,411	$ 4,411
Reissuance of treasury stock for stock-based compensation and other (in shares)				11,464
Reissuance of treasury stock for stock-based compensation and other		999		$ 1,000	0				(1)
Capital activities by noncontrolling interests		(11,372)							(11,372)	(11,372)							(11,372)
Ending balance (in shares) at Jun. 30, 2018			(111,990,222)	(17,633)							(71,264,947)
Balance at end of period at Jun. 30, 2018		$ 5,159,434	$ 2,624,672	$ (1,431)	2,465,402		(56,624)		127,415	5,412,930	$ 178,162	2,571,696	2,570,816		(35,159)		127,415
Beginning balance (in shares) at Dec. 31, 2018		(112,159,896)	(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 loss		72					72			(169)					(169)
Dividends on common stock		(165,626)			(165,626)					(165,598)			(165,598)
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				0
Capital activities by noncontrolling interests		$ (11,372)							(11,372)	(11,372)							(11,372)
Ending balance (in shares) at Jun. 30, 2019		(112,361,595)	(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 loss		(1,135)					(1,135)			(1,249)					(1,249)
Dividends on common stock		(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				0
Capital activities by noncontrolling interests		$ (11,372)							(11,372)	(11,372)							(11,372)
Ending balance (in shares) at Jun. 30, 2019		(112,361,595)	(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

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

[2] In 2018, the Company adopted new accounting guidance and elected to reclassify income tax effects of the Tax Cuts and Jobs Act of 2017 (the “Tax Act”) on items within accumulated other comprehensive income to retained earnings.

[3] In 2018, the Company adopted new accounting guidance and elected to reclassify income tax effects of the Tax Act on items within accumulated other comprehensive income to retained earnings.