Basic and Diluted Earnings Per Share (Detail) - USD ($) $ / shares in Units, shares in Millions, $ in Millions		3 Months Ended
		Dec. 31, 2016	Dec. 31, 2015
Schedule of Earnings Per Share, Basic and Diluted, by Common Class [Line Items]
Net income	[1]	$ 2,070	$ 1,941
Class A common stock
Schedule of Earnings Per Share, Basic and Diluted, by Common Class [Line Items]
Income Allocation (A)	[1]	$ 1,594	$ 1,550
Weighted- Average Shares Outstanding (B)		1,860	1,937
Earnings per Share (A)/(B)	[2]	$ 0.86	$ 0.80
Income Allocation (A)	[1]	$ 2,070	$ 1,941
Weighted- Average Shares Outstanding (B)	[3]	2,421	2,430
Earnings per Share (A)/(B)	[2]	$ 0.86	$ 0.80
Class B common stock
Schedule of Earnings Per Share, Basic and Diluted, by Common Class [Line Items]
Income Allocation (A)	[1]	$ 347	$ 324
Weighted- Average Shares Outstanding (B)		245	245
Earnings per Share (A)/(B)	[2]	$ 1.41	$ 1.32
Income Allocation (A)	[1]	$ 346	$ 323
Weighted- Average Shares Outstanding (B)		245	245
Earnings per Share (A)/(B)	[2]	$ 1.41	$ 1.32
Class C common stock
Schedule of Earnings Per Share, Basic and Diluted, by Common Class [Line Items]
Income Allocation (A)	[1]	$ 57	$ 63
Weighted- Average Shares Outstanding (B)		17	20
Earnings per Share (A)/(B)	[2]	$ 3.43	$ 3.20
Income Allocation (A)	[1]	$ 57	$ 63
Weighted- Average Shares Outstanding (B)		17	20
Earnings per Share (A)/(B)	[2]	$ 3.42	$ 3.20
Participating securities
Schedule of Earnings Per Share, Basic and Diluted, by Common Class [Line Items]
Income Allocation (A)	[1],[4]	$ 72	$ 4
Income Allocation (A)	[1],[4]	$ 72	$ 4

[1] Net income is allocated based on proportional ownership on an as-converted basis. The weighted-average number of shares of as-converted class B common stock used in the income allocation was 405 million for the three months ended December 31, 2016 and 2015. The weighted-average number of shares of as-converted class C common stock used in the income allocation was 67 million and 78 million for the three months ended December 31, 2016 and 2015, respectively. The weighted-average number of shares of as-converted U.K.&I and Europe preferred stock, included within participating securities, used in the income allocation was 35 million and 44 million, respectively, for the three months ended December 31, 2016.

[2] Figures in the table may not recalculate exactly due to rounding. Earnings per share is calculated based on unrounded numbers.

[3] Weighted-average diluted shares outstanding are calculated on an as-converted basis, and include incremental common stock equivalents, as calculated under the treasury stock method. The computation includes approximately 5 million common stock equivalents for the three months ended December 31, 2016 and 2015 because their effect would be dilutive. The computation excludes 3 million and 1 million of common stock equivalents for the three months ended December 31, 2016 and 2015, respectively, because their effect would have been anti-dilutive.

[4] Participating securities include preferred stock outstanding and unvested share-based payment awards that contain non-forfeitable rights to dividends or dividend equivalents, such as the Company's U.K.&I and Europe preferred stock, restricted stock awards, restricted stock units and earned performance-based shares. Participating securities' income is allocated based on the weighted-average number of shares of as-converted stock.