Environmental Commitments and Contingencies (Details Textual) (USD $)	6 Months Ended
	Jun. 30, 2012 Property	Jun. 30, 2011	Dec. 31, 2011
Environmental Commitments and Contingencies (Textual) [Abstract]
Environmental liabilities	$ 9,298,000		$ 9,492,000
Amount paid for funding requirements	194,000	326,000
Environmental Commitments and Contingencies (Additional Textual) [Abstract]
Company's exposure in number of former Manufactured Gas Plant Sites	6
FPU [Member]
Environmental Commitments and Contingencies (Textual) [Abstract]
Environmental liabilities	10,900,000
Approval of recovery of environmental costs	14,000,000
Environmental costs recovered	8,500,000
Chesapeake [Member]
Environmental Commitments and Contingencies (Textual) [Abstract]
Environmental liabilities	223,000
Regulatory assets for future recovery of environmental costs	792,000
Manufactured Gas Plant [Member] | FPU [Member]
Environmental Commitments and Contingencies (Textual) [Abstract]
Regulatory assets for future recovery of environmental costs	5,500,000
West Palm Beach Florida [Member]
Environmental Commitments and Contingencies (Textual) [Abstract]
Estimated costs of remediation range, minimum	4,600,000
Estimated costs of remediation range, maximum	15,700,000
Sanford Florida [Member]
Environmental Commitments and Contingencies (Textual) [Abstract]
Estimated costs of remediation range, maximum	13,000,000
Cost of remedy for settlements of claims	20,000,000
Costs to resolve liability	650,000
Sanford Florida [Member] | FPU [Member]
Environmental Commitments and Contingencies (Textual) [Abstract]
Estimated costs of remediation range, maximum	650,000
Environmental remediation expense percent	5.00%
Amount paid for funding requirements	650,000
Environmental Remediation Expense	24,000
Key West Florida [Member]
Environmental Commitments and Contingencies (Textual) [Abstract]
Period of regulatory inactivity	17 years
Key West Florida [Member] | Maximum [Member]
Environmental Commitments and Contingencies (Textual) [Abstract]
Costs to resolve liability	100,000
Pensacola Florida [Member] | Maximum [Member]
Environmental Commitments and Contingencies (Textual) [Abstract]
Costs to resolve liability	5,000
Salisbury Maryland [Member] | Maximum [Member]
Environmental Commitments and Contingencies (Textual) [Abstract]
Monitoring well remaining maximum cost	5,000
Winter Haven Florida [Member]
Environmental Commitments and Contingencies (Textual) [Abstract]
Operating and monitoring system cost	46,000
Cost of excavation	250,000
Corrective measures cost	$ 1,000,000
Winter Haven Florida [Member] | Maximum [Member]
Environmental Commitments and Contingencies (Textual) [Abstract]
Remedial action time period	3 years
Winter Haven Florida [Member] | Minimum [Member]
Environmental Commitments and Contingencies (Textual) [Abstract]
Remedial action time period	2 years