Financing Arrangements (Details 1) (USD $) In Millions, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
Long-term debt
Current portion of long-term debt	$ 12.2	$ 14.3
Long-term debt	473.9	478.8
Total Long-term debt	486.1	493.1
Series A Medium Term Note [Member]
Long-term debt
Total Long-term debt	175.0	175.0
Senior Unsecured Notes [Member]
Long-term debt
Total Long-term debt	249.8	249.8
Ohio Water Development Revenue Refunding Bonds [Member]
Long-term debt
Total Long-term debt	12.2	12.2
Ohio Air Quality Development Revenue Refunding Bonds [Member]
Long-term debt
Total Long-term debt	9.5	9.5
Ohio Pollution Control Revenue Refunding Bonds [Member]
Long-term debt
Total Long-term debt	17.0	17.0
Credit Facility with US Bank for AGC [Member]
Long-term debt
Total Long-term debt	1.7	5.1
Other Long Term Debt [Member]
Long-term debt
Total Long-term debt	$ 20.9	$ 24.5