Risk Management (Narrative) (Details) - Price Risk Contracts Member - Maximum	6 Months Ended
Jun. 30, 2020
Derivative [Line Items]
Remaining maturity	37 months
Percent of contracts expiring in the next twelve months	83.00%

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

No definition available.

Name:	us-gaap_DerivativeLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration