Stock Based Compensation (Narrative) (Details) (USD $) In Millions, except Share data, unless otherwise specified	6 Months Ended	12 Months Ended		6 Months Ended						1 Months Ended		6 Months Ended
	Mar. 31, 2013	Sep. 30, 2012	Sep. 30, 2011	Mar. 31, 2013 Restricted Stock Units (RSUs) [Member]	Mar. 31, 2012 Restricted Stock Units (RSUs) [Member]	Mar. 31, 2013 Restricted Stock Units (RSUs) [Member] Time Based Restricted Stock Unit [Member]	Mar. 31, 2013 Restricted Stock Units (RSUs) [Member] Performance Based Restricted Stock Unit [Member]	Mar. 31, 2013 Additional Restricted Stock Units [Member]	Mar. 31, 2012 Additional Restricted Stock Units [Member]	Feb. 28, 2013 Restricted Stock [Member]	Jan. 31, 2013 Restricted Stock [Member]	Mar. 31, 2013 Restricted Stock [Member]	Mar. 31, 2012 Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Actual amount of RSUs earned based on cumulative earnings							60.00%
Target RSUs granted range						40.00%
Vesting percentage per year												50.00%
Units outstanding	123,980	99,725	69,378
Performance cycle							3 years
Vesting period					3 years	3 years			3 years			2 years
Shares granted during period	58,775	54,825		35,265	32,894			23,510	21,931
Shares issued under the plan										16,000	500
Shares issued, price per share										$ 58.54	$ 42.54
Weighted average grant date fair value		$ 38.71		$ 38.82	$ 31.18			$ 38.82	$ 31.18
Compensation expense				$ 1.5	$ 0.2							$ 1.1	$ 0.3