Segment Information - Additional Information (Detail)	Dec. 31, 2015 Customer
Tampa Electric [Member] | Tampa Electric Company [Member]
Segment Reporting Information [Line Items]
Number of retail electric utility service customers in West Central Florida	719,000
Tampa Electric [Member] | Minimum [Member]
Segment Reporting Information [Line Items]
Number of retail electric utility service customers in West Central Florida	719,000
PGS [Member] | Minimum [Member]
Segment Reporting Information [Line Items]
Number of residential, commercial, industrial and power generation customers for natural gas purchase and distribution	361,000
PGS [Member] | Minimum [Member] | Tampa Electric Company [Member]
Segment Reporting Information [Line Items]
Number of residential, commercial, industrial and power generation customers for natural gas purchase and distribution	361,000
NMGC [Member] | Minimum [Member]
Segment Reporting Information [Line Items]
Number of residential, commercial, industrial and power generation customers for natural gas purchase and distribution	516,000