Nature of Operations and Basis of Consolidation (Details) $ in Millions	12 Months Ended
Dec. 31, 2018 USD ($) watts customers	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Number of customers \| customers	726,400
Number of megawatts of qualifying facility \| watts	35
Estimated aggregate gross contractual payments through 2024	$ 171.0
Variable interest entity, measure of activity, purchases	$ 25.6	$ 16.3	$ 25.5

The amount of purchases between the reporting entity and the Variable Interest Entity (VIE).

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 810
-SubTopic 10
-Section 50
-Paragraph 6
-Subparagraph d
-URI http://asc.fasb.org/extlink&oid=108788376&loc=d3e5747-111685

Name:	us-gaap_VariableInterestEntityActivityBetweenVIEAndEntityPurchases
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration