Financial Instruments and Risk Management (Narrative) (Details) barrels_per_day in Thousands, $ in Millions	6 Months Ended			12 Months Ended	24 Months Ended
	Jun. 30, 2021 USD ($) barrels_per_day contract OffsettingPosition $ / bbl	Dec. 31, 2020 barrels_per_day OffsettingPosition $ / bbl	Jun. 30, 2020 barrels_per_day contract $ / bbl	Dec. 31, 2021 barrels_per_day $ / bbl	Dec. 31, 2019 Acquisition
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Amount of loss reclassified to interest expense | $	$ (2.1)
Number of foreign currency derivatives (in contracts) | contract	0		0
Number of businesses acquired (in acquisitions) | Acquisition					2
Number of offsetting positions (in offsetting positions) | OffsettingPosition	0	0
Commodity derivative contracts
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Daily production commitment (barrels per day) | barrels_per_day	45	2	45
Average forward price (in dollars per barrel) | $ / bbl	42.77	41.54	56.42
Forecast | Commodity derivative contracts
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Average forward price (in dollars per barrel) | $ / bbl				44.88
Forecast | Commodity derivative contracts | Subsequent Event
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Daily production commitment (barrels per day) | barrels_per_day				20