Property, Plant And Equipment (Schedule Of Property, Plant And Equipment) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2014		Dec. 31, 2013
Property, Plant and Equipment [Line Items]
Property Plant and Equipment	$ 25,642.1		$ 23,664.2
Accumulated Depreciation and Amortization	(9,625.0)		(9,299.1)
Net Property, Plant and Equipment	16,017.1		14,365.1
Gas Distribution Utility [Member]
Property, Plant and Equipment [Line Items]
Property Plant and Equipment	9,753.9	[1]	8,927.4	[1]
Accumulated Depreciation and Amortization	(2,922.7)	[1]	(2,868.7)	[1]
Gas Transmission Utility [Member]
Property, Plant and Equipment [Line Items]
Property Plant and Equipment	7,181.1		6,669.0
Accumulated Depreciation and Amortization	(2,953.5)		(2,879.0)
Electric Utility [Member]
Property, Plant and Equipment [Line Items]
Property Plant and Equipment	7,160.0	[1]	6,815.0	[1]
Accumulated Depreciation and Amortization	(3,596.5)	[1]	(3,426.4)	[1]
Common Utility [Member]
Property, Plant and Equipment [Line Items]
Property Plant and Equipment	179.1		163.5
Accumulated Depreciation and Amortization	(105.9)		(82.4)
Construction Work In Process [Member]
Property, Plant and Equipment [Line Items]
Property Plant and Equipment	960.7		728.8
Non-Utility And Other [Member]
Property, Plant and Equipment [Line Items]
Property Plant and Equipment	407.3	[2]	360.5	[2]
Accumulated Depreciation and Amortization	$ (46.4)	[2]	$ (42.6)	[2]

[1] NIPSCO’s common utility plant and associated accumulated depreciation and amortization are allocated between Gas Distribution Utility and Electric Utility Property, Plant and Equipment.

[2] Non-Utility and Other includes the property, plant and equipment of Columbia Pipeline Group's unregulated businesses.