Basic and Diluted Earnings Per Share - Additional Information (Detail) shares in Millions		3 Months Ended		9 Months Ended
	Mar. 19, 2015	Jun. 30, 2015 shares	Jun. 30, 2014 shares	Jun. 30, 2015 shares	Jun. 30, 2014 shares
Schedule of Earnings Per Share, Basic and Diluted, by Common Class [Line Items]
Stock options included in the computation of diluted shares outstanding		5	6	5	7
Stock Options
Schedule of Earnings Per Share, Basic and Diluted, by Common Class [Line Items]
Stock options excluded from computation of average dilutive shares outstanding		1	1	2	2
Class A common stock
Schedule of Earnings Per Share, Basic and Diluted, by Common Class [Line Items]
Stock split, conversion ratio	4
Class B common stock
Schedule of Earnings Per Share, Basic and Diluted, by Common Class [Line Items]
Weighted-average as-converted class B common stock used in income allocation		405	413	405	413
Class C common stock
Schedule of Earnings Per Share, Basic and Diluted, by Common Class [Line Items]
Weighted-average as-converted class B common stock used in income allocation		78	103	82	104