Stock-Based Compensation Plans (Fair Value Assumptions) (Details) (USD $)	12 Months Ended
Sep. 30, 2011 years	Sep. 30, 2010 years	Sep. 30, 2009 years
Stock-Settled Stock Appreciation Rights [Member]
Expected term, years	6.0	6.1	7.0
Expected stock price volatility	30.00%	30.40%	30.50%
Risk-free interest rate	1.74%	2.07%	2.70%
Expected dividends	0.00%	0.00%	0.00%
Fair value (per right)	$ 20.26	$ 19.19	$ 22.68
Cash-Settled Stock Appreciation Rights [Member]
Expected term, years	5.0	6.0
Expected stock price volatility	30.00%	30.00%
Risk-free interest rate	0.96%	1.58%
Expected dividends	0.00%	0.00%
Fair value (per right)	$ 30.27	$ 19.16

The period of time an equity-based award is expected to be outstanding. An equity-based award's expected term is generally determined based on, among other factors, the instrument's contractual term and the effects of employees' expected exercise and post-vesting employment termination behavior.

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The estimated measure of the percentage by which a share price is expected to fluctuate during a period. Volatility also may be defined as a probability-weighted measure of the dispersion of returns about the mean. The volatility of a share price is the standard deviation of the continuously compounded rates of return on the share over a specified period. That is the same as the standard deviation of the differences in the natural logarithms of the stock prices plus dividends, if any, over the period.

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