Rates and Other Regulatory Activities - Additional Information (Detail) (Florida [Member], USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2013 Customer
Florida [Member]
Investment In Affiliates [Line Items]
Period to replace qualifying mains and services	10 years
Duration of right to give notice to FPU	180 days
Duration of closing of the purchase	12 months
Loss of earnings generated by FPU from number of customers	3,000
Period of current agreement exceeds	2 years
Expiration date	Dec. 31, 2019
Amortization period of regulatory asset	Five years
Litigation expense	$ 1.6