Goodwill and Other Intangibles - Additional Information (Details) $ in Millions	3 Months Ended	6 Months Ended
	Mar. 31, 2018 USD ($)	Mar. 31, 2018 USD ($)
Goodwill and Intangible Assets Disclosure [Abstract]
Other intangible assets, net of accumulated amortization	$ 39	$ 39
Accumulated amortization on intangible assets	6	6
Amortization expense on intangible assets	$ 2	$ 2