Basic and Diluted Earnings Per Share (Detail) - USD ($) $ / shares in Units, shares in Millions, $ in Millions		3 Months Ended		9 Months Ended
		Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Schedule of Earnings Per Share, Basic and Diluted, by Common Class [Line Items]
Net income		$ 2,329	$ 2,059	$ 7,456	$ 4,559
Class A common stock
Schedule of Earnings Per Share, Basic and Diluted, by Common Class [Line Items]
Income Allocation - Basic	[1]	$ 1,793	$ 1,591	$ 5,746	$ 3,518
Weighted- Average Shares Outstanding - Basic		1,784	1,840	1,798	1,852
Earnings per Share - Basic	[2]	$ 1.00	$ 0.87	$ 3.20	$ 1.90
Income Allocation - Diluted	[1]	$ 2,329	$ 2,059	$ 7,456	$ 4,559
Weighted- Average Shares Outstanding - Diluted	[3]	2,321	2,385	2,337	2,404
Earnings per Share - Diluted	[2]	$ 1.00	$ 0.86	$ 3.19	$ 1.90
Class B common stock
Schedule of Earnings Per Share, Basic and Diluted, by Common Class [Line Items]
Income Allocation - Basic	[1]	$ 406	$ 350	$ 1,293	$ 769
Weighted- Average Shares Outstanding - Basic		245	245	245	245
Earnings per Share - Basic	[2]	$ 1.66	$ 1.43	$ 5.27	$ 3.13
Income Allocation - Diluted	[1]	$ 406	$ 349	$ 1,291	$ 767
Weighted- Average Shares Outstanding - Diluted		245	245	245	245
Earnings per Share - Diluted	[2]	$ 1.65	$ 1.42	$ 5.26	$ 3.13
Class C common stock
Schedule of Earnings Per Share, Basic and Diluted, by Common Class [Line Items]
Income Allocation - Basic	[1]	$ 49	$ 47	$ 159	$ 114
Weighted- Average Shares Outstanding - Basic		12	14	12	15
Earnings per Share - Basic	[2]	$ 4.02	$ 3.46	$ 12.78	$ 7.60
Income Allocation - Diluted	[1]	$ 49	$ 47	$ 158	$ 114
Weighted- Average Shares Outstanding - Diluted		12	14	12	15
Earnings per Share - Diluted	[2]	$ 4.01	$ 3.45	$ 12.76	$ 7.59
Participating securities
Schedule of Earnings Per Share, Basic and Diluted, by Common Class [Line Items]
Income Allocation - Basic	[1],[4]	$ 81	$ 71	$ 258	$ 158
Income Allocation - Diluted	[1],[4]	$ 81	$ 71	$ 259	$ 158

[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 and nine months ended June 30, 2018 and 2017. The weighted-average number of shares of as-converted class C common stock used in the income allocation was 49 million and 50 million for the three and nine months ended June 30, 2018, respectively, and 54 million and 60 million for the three and nine months ended June 30, 2017, respectively. The weighted-average number of shares of preferred stock included within participating securities was 32 million of as-converted UK&I preferred stock for the three and nine months ended June 30, 2018, and 33 million and 34 million of as-converted UK&I preferred stock for the three and nine months ended June 30, 2017, respectively. The weighted-average number of shares of preferred stock included within participating securities was 44 million of as-converted Europe preferred stock for the three and nine months ended June 30, 2018 and 2017.

[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 3 million common stock equivalents for the three and nine months ended June 30, 2018, and 4 million and 5 million common stock equivalents for the three and nine months ended June 30, 2017, respectively, because their effect would be dilutive. The computation excludes less than 1 million and 1 million of common stock equivalents for the three and nine months ended June 30, 2018, respectively, and less than 1 million and 3 million of common stock equivalents for the three and nine months ended June 30, 2017, 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 UK&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.