Defined Benefit Pension and Other Postretirement Plans (Details Textuals) (USD $) In Millions, unless otherwise specified	3 Months Ended	1 Months Ended	3 Months Ended	9 Months Ended	3 Months Ended		9 Months Ended
	Dec. 31, 2010	Dec. 31, 2010 Pension Benefit [Member]	Dec. 31, 2010 Pension Benefit [Member]	Jun. 30, 2011 Pension Benefit [Member]	Jun. 30, 2011 Non-qualified Supplemental Executive Retirement Plan [Member]	Jun. 30, 2010 Non-qualified Supplemental Executive Retirement Plan [Member]	Jun. 30, 2011 Non-qualified Supplemental Executive Retirement Plan [Member]	Jun. 30, 2010 Non-qualified Supplemental Executive Retirement Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Expected contribution to pensions plans in next twelve months				$ 16.0
Pension and other postretirement plans pretax expense					0.9	0.6	2.2	1.8
Contribution to the Pension Plan	1.8			16.7
Decrease in other noncurrent liabilities on remeasurement of merged plan's assets and benefit obligations		46.7	46.7
Decrease in regulatory assets on remeasurement of merged plan's assets and benefit obligations	43.1		43.1
Increase in pre-tax other comprehensive income on remeasurement of merged plan's assets and benefit obligations			3.6
Discount rate for the merged plan		5.50%	5.50%
Accumulated benefit obligation of the merged plan		$ 391.2	$ 391.2
Expected rate of return on plan assets		8.50%
Rate of increase in salary levels		3.80%