Related Party Transactions (Details) (Tax Allocation Agreement, Capistrano Wind Holdings, Affiliated Entity, USD $) In Millions, unless otherwise specified	Dec. 31, 2014
Tax Allocation Agreement \| Capistrano Wind Holdings \| Affiliated Entity
Related Party Transaction [Line Items]
Due to affiliate under tax allocation agreements	$ 184

Carrying amount as of the balance sheet date of obligations due all related parties.

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