Asset Retirement Obligation (Details) $ in Millions	3 Months Ended
Mar. 31, 2019 USD ($)
Saratoga Wind Farm [Member]
Asset Retirement Obligations [Roll Forward]
Saratoga Wind Asset Retirement Obligation	$ 1.5

Amount of asset retirement obligations incurred during the period.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 410
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (c)(1)
-URI http://asc.fasb.org/extlink&oid=6392692&loc=d3e7535-110849

Name:	us-gaap_AssetRetirementObligationLiabilitiesIncurred
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration