Commitments and Contingencies (Details) (Manufactured Gas Plant Sites [Member], USD $) In Millions, unless otherwise specified	6 Months Ended
	Jun. 30, 2013
Manufactured Gas Plant Sites [Member]
Commitments and Contingencies [Line Items]
Loss Contingency, Range of Possible Loss, Minimum	$ 16
Loss Contingency, Range of Possible Loss, Maximum	62
Period for future costs of detailed site investigation and remediation costs	over the next ten years
Accrual for Environmental Loss Contingencies, Provision for New Losses	$ 38.2