Income Taxes (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2012	Dec. 31, 2011
Income Taxes
Total income tax expense	$ 16.4	$ 14.7	$ 35.9	$ 27.2
Income tax expense as a percent of pre-tax income	33.10%	38.20%	33.10%	36.40%