Subsequent Event (Details) $ in Millions	3 Months Ended
Mar. 31, 2018 USD ($) MW	Mar. 31, 2017 USD ($)	Dec. 31, 2016 MW
Subsequent Event [Line Items]
Power Volume \| MW	220		10
Taxes, Miscellaneous \| $	$ 446	$ 436

All taxes not related to income of the entity or excise or sales taxes levied on the revenue of the entity that are not reported elsewhere. These taxes could include production, real estate, personal property, and pump tax.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 225
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.9)
-URI http://asc.fasb.org/extlink&oid=63488584&loc=d3e20235-122688

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