Retirement Plans and Other Benefits (Details) (USD $) In Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010
Pinnacle West | Pension Benefits
Net periodic benefit costs and the portion of these costs charged to expense
Net periodic benefit cost charged to expense	$ 7	$ 10	$ 22	$ 29
Pension Benefits
Net periodic benefit costs and the portion of these costs charged to expense
Service cost - benefits earned during the period	14	14	43	42
Interest cost on benefit obligation	31	31	94	92
Expected return on plan assets	(33)	(31)	(100)	(93)
Amortization of prior service cost			1	1
Amortization of net actuarial loss	7	5	19	15
Net periodic benefit cost	19	19	57	57
Contributions
Expected contribution to benefit plans in the current fiscal year	0		0
Expected contributions for next fiscal period	68		68
Pinnacle West | Other Benefits
Net periodic benefit costs and the portion of these costs charged to expense
Net periodic benefit cost charged to expense	4	4	12	12
Other Benefits
Net periodic benefit costs and the portion of these costs charged to expense
Service cost - benefits earned during the period	5	4	17	14
Interest cost on benefit obligation	12	11	35	32
Expected return on plan assets	(10)	(9)	(31)	(29)
Amortization of net actuarial loss	4	2	11	7
Net periodic benefit cost	11	8	32	24
Contributions
Expected contribution to benefit plans in the current fiscal year	20		20
Expected contributions for next fiscal period	$ 20		$ 20