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Basic and Diluted Earnings Per Share - Additional Information (Detail)
In Millions, unless otherwise specified
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3 Months Ended |
6 Months Ended |
0 Months Ended |
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Mar. 31, 2015
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Mar. 31, 2014
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Mar. 31, 2015
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Mar. 31, 2014
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Mar. 19, 2015
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| Schedule of Earnings Per Share, Basic and Diluted, by Common Class [Line Items] |
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| Stock options included in the computation of diluted shares outstanding |
5 |
7 |
5 |
7 |
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| Stock Options |
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| Schedule of Earnings Per Share, Basic and Diluted, by Common Class [Line Items] |
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| Stock options excluded from computation of average dilutive shares outstanding |
1 |
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1 |
2 |
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| Stock Options | Maximum |
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| Schedule of Earnings Per Share, Basic and Diluted, by Common Class [Line Items] |
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| Stock options excluded from computation of average dilutive shares outstanding |
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1 |
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| Class A common stock |
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| Schedule of Earnings Per Share, Basic and Diluted, by Common Class [Line Items] |
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| Stock split, conversion ratio |
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4 |
| Class B common stock |
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| Schedule of Earnings Per Share, Basic and Diluted, by Common Class [Line Items] |
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| Weighted-average as-converted class B common stock used in income allocation |
405 |
413 |
405 |
413 |
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| Class C common stock |
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| Schedule of Earnings Per Share, Basic and Diluted, by Common Class [Line Items] |
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| Weighted-average as-converted class B common stock used in income allocation |
81 |
104 |
84 |
105 |
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