Revenue Remaining Performance Obligations (Policies)	12 Months Ended
	Dec. 31, 2018
Remaining Performance Obligations [Abstract]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Table Text Block]	Remaining Performance Obligations — The transaction price allocated to remaining performance obligations represents future consideration for unsatisfied (or partially unsatisfied) performance obligations at the end of the reporting period. As of December 31, 2018, the aggregate amount of transaction price allocated to remaining performance obligations was $15 million, primarily consisting of fixed consideration for the sale of renewable energy credits (RECs) in long-term contracts in the U.S. We expect to recognize revenue on approximately one-fifth of the remaining performance obligations in 2019, with the remainder recognized thereafter. The Company has elected to apply the optional disclosure exemptions under ASC 606. Therefore, the amount above excludes contracts with an original length of one year or less, contracts for which we recognize revenue based on the amount we have the right to invoice for services performed, and variable consideration allocated entirely to a wholly unsatisfied performance obligation when the consideration relates specifically to our efforts to satisfy the performance obligation and depicts the amount to which we expect to be entitled. As such, consideration for energy is excluded from the amounts above as the variable consideration relates to the amount of energy delivered and reflects the value the Company expects to receive for the energy transferred. Estimates of revenue expected to be recognized in future periods also exclude unexercised customer options to purchase additional goods or services that do not represent material rights to the customer.