Summary of Significant Accounting Policies and Procedures - Summary of MyPower Deferred Cost Activity (Parenthetical) (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
MyPower Program [Member]
Summary Of Significant Accounting Policies And Recent Accounting Pronouncements [Line Items]
Deferred contract origination cost	$ 27.2	$ 0.0