Guarantees	12 Months Ended
Dec. 31, 2017
Guarantees [Abstract]
Guarantees	Guarantees In connection with the sale of its NORESCO domestic operations in December 2005, the Company agreed to maintain in place guarantees of certain warranty obligations of NORESCO. The savings guarantees provided that once the energy-efficiency construction was completed by NORESCO, the customer would experience a certain dollar amount of energy savings over a period of years. The undiscounted maximum aggregate payments that may be due related to these guarantees were approximately $95 million as of December 31, 2017, extending at a decreasing amount for approximately 11 years. See Note 12 for discussion of the MVP Joint Venture guarantee.

Guarantees

12 Months Ended

Dec. 31, 2017

In connection with the sale of its NORESCO domestic operations in December 2005, the Company agreed to maintain in place guarantees of certain warranty obligations of NORESCO. The savings guarantees provided that once the energy-efficiency construction was completed by NORESCO, the customer would experience a certain dollar amount of energy savings over a period of years. The undiscounted maximum aggregate payments that may be due related to these guarantees were approximately $95 million as of December 31, 2017, extending at a decreasing amount for approximately 11 years.

See Note 12 for discussion of the MVP Joint Venture guarantee.