Stock Based Compensation (Narrative) (Details) (USD $) In Millions, except Share data, unless otherwise specified	9 Months Ended	12 Months Ended	3 Months Ended		9 Months Ended		15 Months Ended	9 Months Ended		3 Months Ended		1 Months Ended		9 Months Ended
	Jun. 30, 2013	Sep. 30, 2012	Dec. 31, 2012 Restricted Stock Units (RSUs) [Member]	Dec. 31, 2011 Restricted Stock Units (RSUs) [Member]	Jun. 30, 2013 Restricted Stock Units (RSUs) [Member]	Jun. 30, 2012 Restricted Stock Units (RSUs) [Member]	Dec. 31, 2012 Restricted Stock Units (RSUs) [Member]	Jun. 30, 2013 Restricted Stock Units (RSUs) [Member] Time Based Restricted Stock Unit [Member]	Jun. 30, 2013 Restricted Stock Units (RSUs) [Member] Performance Based Restricted Stock Unit [Member]	Dec. 31, 2012 Additional Restricted Stock Units [Member]	Dec. 31, 2011 Additional Restricted Stock Units [Member]	Feb. 28, 2013 Restricted Stock [Member]	Jan. 31, 2013 Restricted Stock [Member]	Jun. 30, 2013 Restricted Stock [Member]	Jun. 30, 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%
Performance cycle							3 years		3 years
Vesting period			3 years	3 years				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					$ 2.0	$ 0.7								$ 0.9	$ 0.4