Commitments and Contingencies (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Commitments [Abstract]
Future minimum operating lease payments due within one year of the balance sheet date	$ 4.7
Future minimum operating lease payments due within the second year of the balance sheet date	3.8
Future minimum operating lease payments due within the third year of the balance sheet date	2.5
Future minimum operating lease payments due within the fourth year of the balance sheet date	1.5
Future minimum operating lease payments due within the fifth year of the balance sheet date	1.1
Future minimum operating lease payments due within after the fifth year of the balance sheet date	4.3
Total lease expense	6.9	7.3	8.0
Guarantees for Other Unconsolidated Affiliates [Member]
Corporate Guarantees [Abstract]
Maximum exposure by parent company on guarantees.	3.0
Performance Guarantee [Member] | Guarantees for ESG [Member]
Corporate Guarantees [Abstract]
Maximum exposure by parent company on guarantees.	25.0
Performance Guarantees and Product Warranties [Abstract]
Number of surety bonds wholly owned subsidiary has outstanding in role as general contractor (in number of surety bonds)	78
Average face amount of surety bonds wholly owned subsidiary has outstanding	3.6
Maximum face amount of surety bond wholly owned subsidiary had outstanding	25.7
Percent of work completed on projects covered by open surety bonds (in hundredths)	60.00%
Timeframe when significant portion of performance guarantee commitments will be fulfilled	within one year
Performance Guarantee [Member] | Guarantees for Other Unconsolidated Affiliates [Member]
Corporate Guarantees [Abstract]
Maximum exposure by parent company on guarantees.	25.0
Performance Guarantee [Member] | Guarantees for Vectren Source [Member]
Corporate Guarantees [Abstract]
Maximum exposure by parent company on guarantees.	56.0
Other Guarantees Outstanding [Member] | Guarantees for ESG [Member]
Corporate Guarantees [Abstract]
Maximum exposure by parent company on guarantees.	27.0
Financial Standby Letter of Credit [Member] | Guarantees for Other Unconsolidated Affiliates [Member]
Corporate Guarantees [Abstract]
Maximum exposure by parent company on guarantees.	$ 20.0