Annual report pursuant to Section 13 and 15(d)

Equity Method Investments in Affiliate - Summary of Consolidated Financial Position and Results of Operations of Significant Holding Companies, Accounted for Using Equity Method (Detail)

v3.3.1.900
Equity Method Investments in Affiliate - Summary of Consolidated Financial Position and Results of Operations of Significant Holding Companies, Accounted for Using Equity Method (Detail) - Strong Upwind Holdings LLC [Member] - USD ($)
$ in Millions
 9 Months Ended 12 Months Ended
Sep. 30, 2015
Dec. 31, 2014
Schedule Of Results Related To Equity Accounted Investees [Line Items]    
Current Assets $ 46 $ 62
Total Assets 1,420 1,501
Current Liabilities 12 18
Total Liabilities 59 66
Members' Equity 1,361 1,435
Revenue 109 154
Income from Continuing Operations 22 44
Net Income $ 22 $ 44