Guarantees and Indemnifications (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2013
Guarantee Of Financial Obligations Of Npt [Member]
Guarantee Obligations [Line Items]
Guarantee Obligations Maximum Exposure	$ 25.0
Various Subsidiary Surety Bonds And Performance Guarantees Expiring Between 2013 And 2015 [Member]
Guarantee Obligations [Line Items]
Guarantee Obligations Maximum Exposure	69.2
Guarantee Of Rocky River Reality And Nusco Lease Payments For Real Estate And Vehicles Expiring 2019 Through 2024 [Member]
Guarantee Obligations [Line Items]
Guarantee Obligations Maximum Exposure	17.7
Guarantee Of Debt Of Ne Hydros [Member]
Guarantee Obligations [Line Items]
Guarantee Obligations Maximum Exposure	$ 3.5