Revenue from Contracts with Customers - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018		Dec. 31, 2017
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	$ 757,000	$ 750,300	$ 680,400	$ 629,400	$ 476,100	$ 475,500	$ 443,000	$ 411,900	$ 2,817,111	$ 1,806,473	[1]	$ 1,300,464	[1]
(Loss) gain on crude contracts									(856)	(41,975)	[1]	9,566	[1]
Gain on sale of assets and other income									12,798	26,903	[1]	133,958	[1]
Total revenues and other income									2,829,053	1,791,401	[1]	1,443,988	[1]
Net crude oil and condensate revenue
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers									2,515,164	1,498,270		1,051,251
Net natural gas liquids revenue
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers									69,584	88,312		56,148
Net natural gas revenue
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers									232,363	219,891		193,065
United States | Net crude oil and condensate revenue
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers									750,278	786,537		644,024
United States | Net natural gas liquids revenue
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers									30,615	61,810		43,804
United States | Net natural gas revenue
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers									27,668	36,070		27,460
United States Offshore | Net crude oil and condensate revenue
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers									1,477,816	417,527		208,984
United States Offshore | Net natural gas liquids revenue
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers									26,968	11,832		6,894
United States Offshore | Net natural gas revenue
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers									46,259	17,559		10,480
Canada | Net crude oil and condensate revenue
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers									116,174	111,836		51,013
Canada | Net natural gas liquids revenue
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers									12,001	14,670		5,450
Canada | Net natural gas revenue
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers									158,436	166,262		155,125
Canada Offshore | Net crude oil and condensate revenue
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers									159,254	176,291		147,230
Other | Net crude oil and condensate revenue
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers									$ 11,642	$ 6,079		$ 0

[1] ¹ Reclassified to conform with current presentation (see Notes C and E). 2017 revenue is presented net of $58.9 million of transportation, gathering and processing costs as historically shown prior to the adoption of ASC 606 on January 1, 2018. See Notes to Consolidated Financial Statements, page 58.