Summary of Significant Accounting Policies - Summary of Noncontrolling Interest Balances (Detail) (USD $)
In Thousands, unless otherwise specified
Sep. 30, 2014
Dec. 31, 2013
Jun. 25, 2014
E1 Arrayan [Member]
Dec. 31, 2013
E1 Arrayan [Member]
Sep. 30, 2014
Noncontrolling Interest [Member]
Dec. 31, 2013
Noncontrolling Interest [Member]
Sep. 30, 2014
Noncontrolling Interest [Member]
Gulf Wind [Member]
Dec. 31, 2013
Noncontrolling Interest [Member]
Gulf Wind [Member]
Sep. 30, 2014
Noncontrolling Interest [Member]
E1 Arrayan [Member]
Dec. 31, 2013
Noncontrolling Interest [Member]
E1 Arrayan [Member]
Sep. 30, 2014
Noncontrolling Interest [Member]
Panhandle 1 [Member]
Dec. 31, 2013
Noncontrolling Interest [Member]
Panhandle 1 [Member]
Noncontrolling Interest [Line Items]                        
Non controlling Interest $ 334,378 $ 99,794     $ 334,378 $ 99,794 $ 89,139 $ 99,794 $ 37,262   $ 207,977  
Percentage of ownership     70.00% 31.50%     60.00% 60.00% 30.00%    21.00%