Debt - Subsidiary Non-recourse Debt in Default or Accelerated (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2014
Nonrecourse Debt Default [Line Items]
Debt Default Amount	$ 1,017
Maritza [Member]
Nonrecourse Debt Default [Line Items]
Net Assets	743
Kavarna [Member]
Nonrecourse Debt Default [Line Items]
Net Assets	91
Covenant Violation [Member] | Maritza [Member]
Nonrecourse Debt Default [Line Items]
Debt Default Amount	820
Covenant Violation [Member] | Kavarna [Member]
Nonrecourse Debt Default [Line Items]
Debt Default Amount	$ 197