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The employer's best estimate, as soon as it can be reasonably determined, of contributions expected to be paid to the plan during the fiscal year 2 beginning after the date of the latest statement of financial position. Estimated contributions may be presented in the aggregate combining (1) contributions required by funding regulations or laws, (2) discretionary contributions, and (3) noncash contributions.

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Percentage of the subsidiary's share of the total cost of the benefit plans relative to the consolidated entity's total cost.

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Actual return on plan assets, separately identifying the amount related to assets still held at the reporting date.

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The increase in the fair value of plan assets from contributions made by the employer.

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The employer's best estimate, as soon as it can be reasonably determined, of contributions expected to be paid to the plan during the next fiscal year beginning after the date of the latest statement of financial position. Estimated contributions may be presented in the aggregate combining (1) contributions required by funding regulations or laws, (2) discretionary contributions, and (3) noncash contributions.

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The amount of the aggregate benefits expected to be paid in the five fiscal years thereafter (the aggregate amount of benefits expected to be paid in years 6 through 10 after the date of the latest statement of financial position).

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The amount of the benefits expected to be paid in Year 5.

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The amount of the benefits expected to be paid in Year 4.

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The amount of the benefits expected to be paid in Year 1.

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The amount of the benefits expected to be paid in Year 3.

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The amount of the benefits expected to be paid in Year 2.

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Assets, usually stocks, bonds, and other investments, that have been segregated and restricted (usually in a trust) to provide benefits, at their fair value as of the measurement date. Plan assets include amounts contributed by the employer (and by employees for a contributory plan) and amounts earned from investing the contributions, less benefits paid. If a plan has liabilities other than for benefits, those non-benefit obligations may be considered as reductions of plan assets.

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Purchases, sales, and settlements of plan assets that occurred during the period.

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Transfers in and out of Level 3. For example, transfers due to changes in the observability of significant inputs.

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The amount of the cost recognized during the period for defined contribution plans.

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Retirement Plans and Other Benefits (Details 4) (USD $)	12 Months Ended
Retirement Plans and Other Benefits (Details 4) (USD $)	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Pinnacle West
Employee Savings Plan Benefits
Expenses recorded for the defined contribution savings plan	$ 8,000,000	$ 9,000,000	$ 9,000,000
ARIZONA PUBLIC SERVICE COMPANY
Employee Savings Plan Benefits
APS's employees share of total cost of the plans (as a percent)	99.00%
Pension Benefits
Changes in fair value for assets that are measured at fair value on a recurring basis
Fair value of plan assets at the beginning of the period		1,461,808,000
Fair value of plan assets at the end of the period	1,850,550,000	1,775,596,000
Contributions
Expected contributions in 2012	65,000,000
Expected contributions in 2013	160,000,000
Expected contributions in 2014	160,000,000
Actual contribution to benefit plans in the current fiscal year		200,000,000
Estimated Future Benefit Payments
2012	113,075,000
2013	122,750,000
2014	132,302,000
2015	141,516,000
2016	154,379,000
Years 2017-2021	941,377,000
Pension Benefits \| Pinnacle West
Changes in fair value for assets that are measured at fair value on a recurring basis
Fair value of plan assets at the end of the period	1,850,550,000	1,775,596,000
Pension Benefits \| ARIZONA PUBLIC SERVICE COMPANY
Contributions
Actual contribution to benefit plans in the current fiscal year		195,000,000
Pension Benefits \| Real estate \| Pinnacle West
Changes in fair value for assets that are measured at fair value on a recurring basis
Fair value of plan assets at the end of the period	106,147,000	92,454,000
Pension Benefits \| Real estate \| Significant Unobservable Inputs (Level 3) \| Pinnacle West
Changes in fair value for assets that are measured at fair value on a recurring basis
Fair value of plan assets at the beginning of the period		64,212,000
Actual return on assets still held		(204,000)
Purchases, sales, and settlements		18,003,000
Transfers in and/or out of Level 3		(82,011,000)
Other Benefits
Changes in fair value for assets that are measured at fair value on a recurring basis
Fair value of plan assets at the beginning of the period	567,410,000	490,455,000
Fair value of plan assets at the end of the period	608,663,000	567,410,000
Contributions
Expected contributions in 2012	20,000,000
Expected contributions in 2013	20,000,000
Expected contributions in 2014	20,000,000
Actual contribution to benefit plans in the current fiscal year	18,769,000	16,700,000
Estimated Future Benefit Payments
2012	27,610,000
2013	30,562,000
2014	33,451,000
2015	36,489,000
2016	39,525,000
Years 2017-2021	246,091,000
Other Benefits \| Pinnacle West
Changes in fair value for assets that are measured at fair value on a recurring basis
Fair value of plan assets at the end of the period	608,663,000	567,410,000
Other Benefits \| ARIZONA PUBLIC SERVICE COMPANY
Contributions
Actual contribution to benefit plans in the current fiscal year	19,000,000	16,000,000	15,000,000
Other Benefits \| Real estate \| Pinnacle West
Changes in fair value for assets that are measured at fair value on a recurring basis
Fair value of plan assets at the end of the period	8,446,000	7,357,000
Other Benefits \| Real estate \| Significant Unobservable Inputs (Level 3) \| Pinnacle West
Changes in fair value for assets that are measured at fair value on a recurring basis
Fair value of plan assets at the beginning of the period		6,504,000
Actual return on assets still held		(23,000)
Purchases, sales, and settlements		45,000
Transfers in and/or out of Level 3		$ (6,526,000)