XML 70 R56.htm IDEA: XBRL DOCUMENT v3.21.1
Income Taxes - Additional Information (Detail) - USD ($)
$ in Millions
3 Months Ended 6 Months Ended
Mar. 31, 2021
Mar. 31, 2020
Dec. 31, 2019
Mar. 31, 2021
Mar. 31, 2020
Income Tax Disclosure [Abstract]          
Release of valuation allowance     $ 33    
Income tax benefit related to release of valuation allowance     $ 33    
Income tax expense (benefit) $ 51 $ (12)   $ 86 $ (7)
Reasonably possible decrease in gross unrecognized tax benefits from ongoing audits and settlement $ 2     $ 2