Income Tax Expense (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Dec. 31, 2011	Dec. 31, 2010
Income Tax Expense [Abstract]
Impact on income tax expense by net research tax credits	$ 0.2	$ 0.4
Effective income tax rate	37.60%	31.60%
Estimated effective income tax rate	34.00%
Increase in effective tax rate	2.40%	2.80%
Reduction in the amount of unrecognized tax benefits in the next twelve months	$ 1.8