Debt Description (Details) In Thousands, unless otherwise specified	12 Months Ended
	Sep. 30, 2012 Bank Of America And Wells Fargo Facilities [Member] USD ($)	Sep. 30, 2012 Wells Fargo Facility [Member] GBP (£)
Maximum Borrowing Capacity	$ 150,000	£ 12,500
Initiation Date	November 1, 2011	November 5, 2010
Termination Date	November 1, 2016
Covenant Terms	The Credit Agreement contains financial covenants, including a fixed charge ratio and a funded debt to EBITDA ratio.	maintain a minimum tangible net worth of £3,000
Interest Rate at Period End	1.10%	1.57%
Interest Rate Description	Under the Third Amendment, the margin on variable interest rate borrowings ranges from 0.95% to 1.50%. The commitment fee under the Third Amendment ranges from 0.15% to 0.25% depending on the funded debt to EBITDA ratio.  The variable interest rate is equal to the Daily LIBOR Floating Rate or the LIBOR 1-month, 2-month, 3-month or 6-month fixed rate (at MWI Co.’s option) plus the margin.	Interest is based on LIBOR for the applicable interest period plus an applicable margin of 1.05% to 1.90%.
Commitment Fee Description	The commitment fee under the Third Amendment ranges from 0.15% to 0.25% depending on the funded debt to EBITDA ratio.