Earnings Per Share (Details) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended
	Dec. 31, 2016 USD ($) director $ / shares shares	Dec. 31, 2015 USD ($) $ / shares shares
Earnings Per Share [Abstract]
Net income | $	$ 72	$ 65
Weighted-average shares used to compute basic EPS (in shares)	205	205
Effect of dilutive securities (in shares)	0	0
Weighted-average shares used to compute diluted EPS (in shares)	205	205
Earnings per share, basic (usd per share) | $ / shares	$ 0.35	$ 0.32
Earnings per share, diluted (usd per share) | $ / shares	$ 0.35	$ 0.32
Number of non-employee directors | director	6