Legislative Matters (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011
Pipeline Safety Law [Member]
Legislative Matters [Line Items]
Estimated amount of operating expenses that could accumulate associated with expanded compliance requirements	$ 9.0
Pipeline Safety Law [Member] | Indiana [Member]
Legislative Matters [Line Items]
Estimated amount of operating expenses that could accumulate associated with expanded compliance requirements	6.0
Capital expenditures driven by the legislation	80.0
Period over which capital expenditures would accumulate (in years)	5
Pipeline Safety Law [Member] | Ohio [Member]
Legislative Matters [Line Items]
Capital expenditures driven by the legislation	55.0
Period over which capital expenditures would accumulate (in years)	5
Indiana House Bill 1004 [Member]
Legislative Matters [Line Items]
Description of legislation	This legislation phases in over four years a two percent rate reduction to the Indiana Adjusted Gross Income Tax for corporations. Pursuant to House Bill 1004, the tax rate will be lowered by one-half percent each year beginning on July 1, 2012, to the final rate of six and one-half percent effective July 1, 2015.
Decrease In Regulatory Asset, Deferred Tax Liabilities	17.1
Indiana Senate Bill 251 [Member]
Legislative Matters [Line Items]
Description of legislation	The legislation establishes a voluntary clean energy portfolio standard that provides incentives to electricity suppliers participating in the program.
Description of the goal of legislation	The law applies to both gas and electric utility operations and provides a framework to recover 80 percent of federally mandated costs through a periodic rate adjustment mechanism outside of a general rate case. Such costs include construction, depreciation, operating and other costs. The remaining 20 percent of those costs are to be deferred for recovery in the utility's next general rate case. The goal of the program is that by 2025, at least 10 percent of the total electricity obtained by the supplier to meet the energy needs of its Indiana retail customers will be provided by clean energy sources, as defined.
Indiana Senate Bill 251 [Abstract]
Power generation capacity for acquired landfill gas generations facility (in megawatts)	3
Long term contract for purchase of electric power generated by wind energy (in megawatts)	50
Purchased electric power generated by wind energy (in megawatts)	30
Percentage of total electricity obtained by the supplier to meet the energy needs of its retail customers provided by clean energy sources (in hundredths)	5.00%
Ohio House Bill 95 [Member]
Legislative Matters [Line Items]
Cost Of Defered Capital Expenditure Program	$ 25.0