Retirement Plans and Other Benefits (Details) (USD $)	3 Months Ended		12 Months Ended		3 Months Ended			12 Months Ended
	Mar. 31, 2011	Mar. 31, 2010	Dec. 31, 2011	Dec. 31, 2010	Mar. 31, 2011 ARIZONA PUBLIC SERVICE COMPANY	Dec. 31, 2011 ARIZONA PUBLIC SERVICE COMPANY	Dec. 31, 2010 ARIZONA PUBLIC SERVICE COMPANY	Dec. 31, 2011 Pension Benefits	Dec. 31, 2010 Pension Benefits	Dec. 31, 2009 Pension Benefits	Dec. 31, 2010 Pension Benefits ARIZONA PUBLIC SERVICE COMPANY	Dec. 31, 2011 Other Benefits	Dec. 31, 2010 Other Benefits	Dec. 31, 2009 Other Benefits	Dec. 31, 2011 Other Benefits ARIZONA PUBLIC SERVICE COMPANY	Dec. 31, 2010 Other Benefits ARIZONA PUBLIC SERVICE COMPANY	Dec. 31, 2009 Other Benefits ARIZONA PUBLIC SERVICE COMPANY
Retirement Plans and Other Benefits
Change in regulatory assets		$ 42,000,000
Increase in accumulated deferred income tax liabilities	(62,000,000)	42,000,000			(62,000,000)
Amount of pension and other postretirement benefit costs deferred			12,000,000
Net periodic benefit costs and the portion of these costs charged to expense
Service cost - benefits earned during the period								57,605,000	59,064,000	54,288,000		21,856,000	19,236,000	18,285,000
Interest cost on benefit obligation								124,727,000	122,724,000	118,282,000		46,807,000	42,428,000	39,180,000
Expected return on plan assets								(133,678,000)	(124,161,000)	(116,535,000)		(41,536,000)	(39,257,000)	(34,428,000)
Amortization of transition obligation												452,000	452,000	3,005,000
Amortization of prior service cost (credit)								1,400,000	1,705,000	2,080,000		(179,000)	(539,000)	(125,000)
Amortization of net actuarial loss								25,956,000	18,833,000	14,216,000		15,015,000	10,317,000	10,320,000
Net periodic benefit cost								76,010,000	78,165,000	72,331,000		42,415,000	32,637,000	36,237,000
Portion of cost charged to expense								29,312,000	37,933,000	36,484,000		15,208,000	15,839,000	18,278,000
Change in Benefit Obligation
Benefit obligation at the beginning of the period								2,345,060,000	2,074,131,000			827,897,000	700,535,000
Service cost								57,605,000	59,064,000	54,288,000		21,856,000	19,236,000	18,285,000
Interest cost								124,727,000	122,724,000	118,282,000		46,807,000	42,428,000	39,180,000
Benefit payments								(104,257,000)	(93,776,000)			(24,877,000)	(20,421,000)
Actuarial loss								275,991,000	183,365,000			171,674,000	98,094,000
Plan amendments									(448,000)			3,737,000	(11,975,000)
Benefit obligation at the end of the period								2,699,126,000	2,345,060,000	2,074,131,000		1,047,094,000	827,897,000	700,535,000
Change in Plan Assets
Fair value of plan assets at the beginning of the period								1,775,596,000	1,461,808,000			567,410,000	490,455,000
Actual return on plan assets								162,042,000	190,380,000			58,367,000	60,255,000
Employer contributions									200,000,000		195,000,000	18,769,000	16,700,000		19,000,000	16,000,000	15,000,000
Benefit payments								(87,088,000)	(76,592,000)			(35,883,000)
Fair value of plan assets at the end of the period								1,850,550,000	1,775,596,000	1,461,808,000		608,663,000	567,410,000	490,455,000
Funded Status at the end of the period								(848,576,000)	(569,464,000)			(438,431,000)	(260,487,000)
Projected benefit obligation and the accumulated benefit obligation for pension plans with an accumulated obligation in excess of plan assets
Projected benefit obligation								2,699,126,000	2,345,060,000
Accumulated benefit obligation								2,396,575,000	2,065,091,000
Fair value of plan assets								1,850,550,000	1,775,596,000
Amounts recognized on the Consolidated Balance Sheets
Current liability								(18,097,000)	(16,830,000)
Noncurrent liability			(1,268,910,000)	(813,121,000)		(1,222,542,000)	(770,611,000)	(830,479,000)	(552,634,000)			(438,431,000)	(260,487,000)
Net amount recognized								$ (848,576,000)	$ (569,464,000)			$ (438,431,000)	$ (260,487,000)