Revenue from Contracts with Customers (Disaggregation of Revenue) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	$ 687,549	$ 425,324	$ 2,038,905	$ 1,311,627
(Loss) gain on derivative instruments	(59,164)	(5,290)	(499,794)	319,502
Gain on sale of assets and other income	2,315	1,831	21,217	6,006
Total revenues and other income	630,700	421,865	1,560,328	1,637,135
Net crude oil and condensate revenue
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	556,620	354,947	1,704,226	1,110,365
Net natural gas liquids revenue
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	31,903	14,311	77,074	35,490
Net natural gas revenue
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	99,026	56,066	257,605	165,772
United States | Net crude oil and condensate revenue
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	167,010	86,498	464,767	272,284
United States | Net natural gas liquids revenue
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	16,356	6,766	33,480	16,145
United States | Net natural gas revenue
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	11,127	4,529	24,442	14,177
United States Offshore | Net crude oil and condensate revenue
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	340,001	216,918	1,079,418	714,143
United States Offshore | Net natural gas liquids revenue
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	11,046	4,765	31,866	13,255
United States Offshore | Net natural gas revenue
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	17,444	9,827	56,855	35,487
Canada     | Net crude oil and condensate revenue
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	29,110	32,358	89,708	67,268
Canada     | Net natural gas liquids revenue
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	4,501	2,780	11,728	6,090
Canada     | Net natural gas revenue
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	70,455	41,710	176,308	116,108
Canada Offshore | Net crude oil and condensate revenue
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	20,499	19,173	70,333	54,864
Other | Net crude oil and condensate revenue
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	$ 0	$ 0	$ 0	$ 1,806