Number of Shares of Class A Common Shares Outstanding on an As-Converted Basis (Detail) shares in Millions |
12 Months Ended | |||||||||||||
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Sep. 30, 2018
conversion_rate
shares
|
Sep. 30, 2017
shares
|
Sep. 30, 2016 |
Sep. 30, 2018
conversion_rate
shares
|
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Class of Stock [Line Items] | ||||||||||||||
As-converted class A common stock | [1] | 2,291 | ||||||||||||
Series B Preferred Stock | ||||||||||||||
Class of Stock [Line Items] | ||||||||||||||
Preferred stock, shares outstanding | 2 | 2 | 2 | |||||||||||
Preferred stock conversion rate | 12.9550 | 13.077 | [2] | 13.952 | ||||||||||
Shares Outstanding As Converted Basis | [1] | 32 | 32 | |||||||||||
Series C Preferred Stock | ||||||||||||||
Class of Stock [Line Items] | ||||||||||||||
Preferred stock, shares outstanding | 3 | 3 | 3 | |||||||||||
Preferred stock conversion rate | 13.8880 | 13.948 | ||||||||||||
Shares Outstanding As Converted Basis | [1] | 44 | 44 | |||||||||||
Class A common stock | ||||||||||||||
Class of Stock [Line Items] | ||||||||||||||
Common stock, shares, outstanding | 1,768 | [3] | 1,818 | 1,768 | [3] | |||||||||
As-converted class A common stock | [1],[3] | 1,768 | ||||||||||||
Class B common stock | ||||||||||||||
Class of Stock [Line Items] | ||||||||||||||
Common stock, shares, outstanding | 245 | 245 | 245 | |||||||||||
Common stock, conversion rate | conversion_rate | [2] | 1.6298 | 1.6298 | |||||||||||
As-converted class A common stock | [1] | 400 | ||||||||||||
Class C common stock | ||||||||||||||
Class of Stock [Line Items] | ||||||||||||||
Common stock, shares, outstanding | 12 | 13 | 12 | |||||||||||
Common stock, conversion rate | conversion_rate | 4.0000 | 4.0000 | ||||||||||||
As-converted class A common stock | [1] | 47 | ||||||||||||
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