Annual report pursuant to Section 13 and 15(d)

The Company - Summary of Unaudited Pro Forma Information (Detail)

v3.3.1.900
The Company - Summary of Unaudited Pro Forma Information (Detail) - American Wind Capital Company, LLC ("AWCC") [Member] - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Business Acquisition, Pro Forma Information, Nonrecurring Adjustment [Line Items]    
Pro forma net investment revenue $ 32 $ 21
Pro forma net income (loss) $ 12 $ (12)