Income Taxes (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Mar. 31, 2017	Mar. 31, 2016
Income Tax Disclosure [Abstract]
Net pre-tax income (loss) tax benefit not recorded	$ (2)	$ 17	$ (3)	$ 28