Summary of Significant Accounting Policies (Policies)	6 Months Ended
Jun. 30, 2012
Accounting Policies [Abstract]
Cash Equivalents	Cash Equivalents Cash equivalents included money market funds totaling $873 million and $1.2 billion at June 30, 2012 and December 31, 2011, respectively. The carrying value of cash equivalents equals the fair value as all investments have original maturities of less than three months.
Restricted Cash and Cash Equivalents	Restricted Cash and Cash Equivalents, and Restricted Deposits Restricted cash and cash equivalents at June 30, 2012 and December 31, 2011 included $97 million received from a wind project financing that was held in escrow at those dates. At June 30, 2012, restricted deposits included $51 million to support outstanding letters of credit issued under EME's letter of credit facilities.
Inventory	Inventory Inventory is stated at the lower of weighted-average cost or market. Inventory is recorded at actual cost when purchased and then expensed at weighted-average cost as used.
Allocation of Net Income or Losses to Investors in Certain Variable Interest Entities	Allocation of Net Income or Losses to Investors in Certain Variable Interest Entities Capistrano Wind Partners' partnership agreements contain complex allocation provisions for taxable income and losses, tax credits and cash distributions. EME allocates net income for this consolidated investment to third-party investors based on the Hypothetical Liquidation Book Value (HLBV) method. HLBV is a balance sheet oriented approach that calculates the change in the claims of each partner on the net assets of the investment at the beginning and end of each period. Each partner's claim is equal to the amount each party would receive or pay if the net assets of the investment were to liquidate at book value and the resulting cash was then distributed to investors in accordance with their respective liquidation preferences. EME reports the net income (loss) attributable to the third-party investors as income (loss) attributable to noncontrolling interests in the consolidated statements of operations. For further information, see Note 3—Variable Interest Entities—Projects or Entities that are Consolidated—Capistrano Wind Equity Capital.

Summary of Significant Accounting Policies (Policies)

6 Months Ended

Jun. 30, 2012

Cash equivalents included money market funds totaling $873 million and $1.2 billion at June 30, 2012 and December 31, 2011, respectively. The carrying value of cash equivalents equals the fair value as all investments have original maturities of less than three months.

Restricted Cash and Cash Equivalents

Restricted Cash and Cash Equivalents, and Restricted Deposits

Restricted cash and cash equivalents at June 30, 2012 and December 31, 2011 included $97 million received from a wind project financing that was held in escrow at those dates. At June 30, 2012, restricted deposits included $51 million to support outstanding letters of credit issued under EME's letter of credit facilities.

Inventory

Inventory is stated at the lower of weighted-average cost or market. Inventory is recorded at actual cost when purchased and then expensed at weighted-average cost as used.

Allocation of Net Income or Losses to Investors in Certain Variable Interest Entities

Capistrano Wind Partners' partnership agreements contain complex allocation provisions for taxable income and losses, tax credits and cash distributions. EME allocates net income for this consolidated investment to third-party investors based on the Hypothetical Liquidation Book Value (HLBV) method. HLBV is a balance sheet oriented approach that calculates the change in the claims of each partner on the net assets of the investment at the beginning and end of each period. Each partner's claim is equal to the amount each party would receive or pay if the net assets of the investment were to liquidate at book value and the resulting cash was then distributed to investors in accordance with their respective liquidation preferences. EME reports the net income (loss) attributable to the third-party investors as income (loss) attributable to noncontrolling interests in the consolidated statements of operations. For further information, see Note 3—Variable Interest Entities—Projects or Entities that are Consolidated—Capistrano Wind Equity Capital.

- Definition

Disclosure of accounting policy for cash and cash equivalents with respect to unrestricted balances.

+ References+ Details

- Definition

Disclosure of accounting policy for consolidation to describe the significant judgments and assumptions made in determining whether a variable interest held by the entity requires the variable interest entity to be consolidated and (or) disclose information about its involvement with the variable interest entity; the methodology used by the entity for determining whether or not it is the primary beneficiary of the variable interest entity; and the significant factors considered and judgments made in determining that the power to direct the activities that significantly impact the economic performance of the variable interest entity are shared (as defined).

+ References

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+ Details

- Definition

Disclosure of accounting policy for major classes of inventories, bases of stating inventories (for example, lower of cost or market), methods by which amounts are added and removed from inventory classes (for example, FIFO, LIFO, or average cost), loss recognition on impairment of inventories, and situations in which inventories are stated above cost. If inventory is carried at cost, this disclosure includes the nature of the cost elements included in inventory.

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