Debt - Subsidiary Non-recourse Debt in Default or Accelerated (Details) (USD $) In Millions, unless otherwise specified	Jun. 30, 2014
Nonrecourse Debt Default [Line Items]
Debt Default Amount	$ 1,010
Maritza [Member]
Nonrecourse Debt Default [Line Items]
Net Assets	572
Kavarna [Member]
Nonrecourse Debt Default [Line Items]
Net Assets	88
Covenant Violation [Member] | Maritza [Member]
Nonrecourse Debt Default [Line Items]
Debt Default Amount	815
Covenant Violation [Member] | Kavarna [Member]
Nonrecourse Debt Default [Line Items]
Debt Default Amount	$ 195