Debt (Other provisions) (Details)	12 Months Ended
Dec. 31, 2018 qtr
Line of Credit Facility [Line Items]
Number of consecutive quarters	4
New Credit Facility \| Minimum
Line of Credit Facility [Line Items]
Current ratio	1.00
New Credit Facility \| Maximum
Line of Credit Facility [Line Items]
Ratio of debt to EBITDAX	4

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