Long-Term Debt and Capital Lease Obligations (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013 Megawatt		Dec. 31, 2012		Dec. 31, 2011	Dec. 31, 2009
Long-term debt outstanding maturities and sinking fund requirements
Next year	$ 322.4
Year 2	399.5
Year 3	27.4
Year 4	29.5
Year 5	281.1
Thereafter	3,566.8
Total	4,626.7
Summary of capitalized leased facilities
Long-term power purchase commitment	140.3		140.3
Accumulated amortization	(92.5)		(86.8)
Total Leased Facilities	47.8		53.5
Future minimum lease payments under capital lease and present value of net minimum lease payments
Due next year	41.9
Due in two years	43.5
Due in three years	45.1
Due in four years	13.9
Due in five years	14.7
Thereafter	56.8
Total Minimum Lease Payments	215.9
Less: Estimated Executory Costs	(61.7)
Capital Leases Future Minimum Payments Due, Less Executory Costs	154.2
Less: Interest	(49.9)
Net Minimum Lease Payments	104.3
Less: Due Currently	(19.8)
Future minimum lease payments under our capital lease and the present value of our net minimum lease payments	84.5
Long-Term Debt and Capital Lease Obligations (Textuals) [Abstract]
Issuance of long-term debt	251.0		251.8		720.0
Number of series of tax-exempt pollution control refunding bonds	2
Restriction under RCC	The RCC provides that we may not redeem, defease or purchase and our subsidiaries may not purchase any Junior Notes on or before May 15, 2037, unless, subject to certain limitations described in the RCC, during the 180 days prior to the date of redemption, defeasance or purchase, we have received a specified amount of proceeds from the sale of qualifying securities.
Period of Power purchase contract with an unaffiliated independent power producer	25 years
Power capacity from a gas-fired cogeneration facility under capital lease (MW)	236
Minimum energy requirement in gas-fired cogeneration facility	0
Power purchase contract expiration year	Dec. 31, 2022
Power purchase contract expected future renewable period	10 years
Total operating lease payment	33.7		32.5
Increase in regulatory asset due to minimum lease payment						78.5
Regulatory asset value at the end of life of contract	0
Total capital lease obligation	104.3		120.0
Capital lease obligation at the end of life of contract	0
Notes (secured, nonrecourse), 6.09% due 2030-2040 [Member]
Long-Term Debt and Capital Lease Obligations (Textuals) [Abstract]
Secured Long-term Debt, Noncurrent	275.0	[1]	275.0	[1]
Debt instrument interest rate stated percentage rate	6.09%		6.09%
Notes (unsecured), 6.20% due 2033 [Member]
Long-Term Debt and Capital Lease Obligations (Textuals) [Abstract]
Unsecured Long-term Debt, Noncurrent	200.0		200.0
Debt instrument interest rate stated percentage rate	6.20%		6.20%
Parent Company [Member]
Long-term debt outstanding maturities and sinking fund requirements
Next year	0
Year 2	0
Year 3	0
Year 4	0
Year 5	0
Thereafter	700.0
Total	700.0
Wisconsin Electric [Member]
Long-Term Debt and Capital Lease Obligations (Textuals) [Abstract]
Unsecured Long-term Debt, Noncurrent	$ 147.0		$ 147.0

[1] (c) Senior notes are secured by a collateral assignment of the leases between ERGSS and Wisconsin Electric related to OC 1 and 2.