Revenue from Contracts with Customers (Disaggregation of Revenue) (Details) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2020	Mar. 31, 2019
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	$ 600,558	$ 629,354
Gain (loss) on crude contracts	400,672	0
Gain on sale of assets and other income	2,498	1,192
Total revenues	1,003,728	630,546
Net crude oil and condensate revenue
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	528,069	551,056
Net natural gas liquids revenue
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	12,563	16,974
Net natural gas revenue
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	59,926	61,324
United States \| Net crude oil and condensate revenue
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	131,236	134,676
United States \| Net natural gas liquids revenue
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	5,503	8,221
United States \| Net natural gas revenue
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	5,558	7,574
United States Offshore \| Net crude oil and condensate revenue
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	346,972	339,663
United States Offshore \| Net natural gas liquids revenue
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	5,026	5,292
United States Offshore \| Net natural gas revenue
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	14,995	4,477
Canada \| Net crude oil and condensate revenue
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	23,383	28,941
Canada \| Net natural gas liquids revenue
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	2,034	3,461
Canada \| Net natural gas revenue
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	39,373	49,273
Canada Offshore \| Net crude oil and condensate revenue
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	24,614	44,924
Other \| Net crude oil and condensate revenue
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	$ 1,864	$ 2,852

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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.

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No definition available.

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Aggregate net gain (loss) on all derivative instruments recognized in earnings during the period, before tax effects.

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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.

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Amount of revenue recognized from goods sold, services rendered, insurance premiums, or other activities that constitute an earning process. Includes, but is not limited to, investment and interest income before deduction of interest expense when recognized as a component of revenue, and sales and trading gain (loss).

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