Inventories (Details) $ in Millions	3 Months Ended
Mar. 31, 2018 USD ($) MBbls	Dec. 31, 2017 MBbls
Inventory [Line Items]
Document Period End Date	Mar. 31, 2018
Energy Related Inventory, Petroleum \| $	$ 9
Crude Oil Inventory \| MBbls	295,000	0

Carrying amount as of the balance sheet date of petroleum or crude oil.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.6(a))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Name:	us-gaap_EnergyRelatedInventoryPetroleum
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant