Exploratory Well Costs (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Capitalized Exploratory Well Costs [Abstract]
Balance at January 1		$ 4,121	$ 2,167	$ 0
Additions Pending the Determination of Proved Reserves		83,175	10,304	27,487
Reclassifications to Proved Properties		(39,325)	(7,917)	(20,802)
Costs Charged to Expense (1)	[1]	(22,074)	(433)	(4,518)
Balance at December 31		$ 25,897	$ 4,121	$ 2,167

[1] Includes capitalized exploratory well costs charged to either dry hole costs or impairments.