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Pension and Postretirement Health and Life Benefits (Narrative) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended		12 Months Ended
	Sep. 30, 2013	Jun. 30, 2013	Jun. 30, 2013	Jun. 30, 2012	Dec. 31, 2012
Curtailment (gains)		$ 0.7
Decrease in pension liability, curtailments		138.3
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Discount Rate		4.92%	4.92%		4.07%
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Rate of Compensation Increase		4.00%	4.00%		4.00%
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Expected Long-term Return on Assets		6.75%			6.75%
Net defined benefit plan costs for former Portsmouth employees			6.3	6.6
Defined Contribution Plan, Employer Matching Contribution, Percent	7.00%		4.00%
Defined Benefit Pension Plans [Member]
Expected defined benefit plan contributions for current fiscal year		23.4	23.4
Expected defined benefit plan contributions for current fiscal year under ERISA		20.9	20.9
Expected defined benefit plan contributions for current fiscal year for non-qualified plans		2.5	2.5
USEC contributions			7.0
Curtailment (gains)		$ 0.7	$ 0.7

X

- Definition

The interest rate used to adjust for the time value of money for the plan.

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Expected rate of compensation increases (for pay-related plans).

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