Revenue Recognition (Disaggregation of Revenue) (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Disaggregation of Revenue
Revenues	$ 1,260,360	$ 1,455,655	$ 1,119,566
Oil sales
Disaggregation of Revenue
Revenues	1,205,083	1,412,358	1,079,703
Natural gas sales
Disaggregation of Revenue
Revenues	6,937	10,231	9,963
CO2 sales and transportation fees
Disaggregation of Revenue
Revenues	34,142	31,145	26,182
Purchased oil sales
Disaggregation of Revenue
Revenues	$ 14,198	$ 1,921	$ 3,718

Amount, excluding tax collected from customer, of revenue from satisfaction of performance obligation by transferring promised good or service to customer. Tax collected from customer is tax assessed by governmental authority that is both imposed on and concurrent with specific revenue-producing transaction, including, but not limited to, sales, use, value added and excise.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 4
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=118956577&loc=SL49130543-203045

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=118956577&loc=SL49130545-203045

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration