Leases (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013 item	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2008 item	Dec. 31, 1986 item
Leases
Lease expense	$ 18	$ 19	$ 21
Estimated future minimum lease payments for operating leases, excluding purchased power agreements
2014	20
2015	17
2016	6
2017	5
2018	4
Thereafter	59
Total future lease commitments	111
APS
Leases
Lease expense	15	16	18
Estimated future minimum lease payments for operating leases, excluding purchased power agreements
2014	17
2015	14
2016	5
2017	5
2018	4
Thereafter	59
Total future lease commitments	$ 104
Number of VIE lessor trusts	3			3	3
Palo Verde Lessor Trusts
Estimated future minimum lease payments for operating leases, excluding purchased power agreements
Number of VIE lessor trusts					3