v3.6.0.2
Assets Held for Sale - Additional Information (Detail) - USD ($)
$ in Millions
12 Months Ended
Feb. 06, 2017
Dec. 31, 2016
Dec. 31, 2015
Dec. 31, 2014
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]        
Cash proceeds   $ 20 $ 1,605 $ 1
SP [Member] | Disposal Group, Held-for-sale, Not Discontinued Operations [Member] | Subsequent Event [Member]        
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]        
Cash proceeds $ 2,750