Supplemental Oil and Gas Disclosures Summary of Operations (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Revenue
Revenues	$ 879,112	$ 909,781	$ 856,396	$ 765,439	$ 663,062	$ 610,506	$ 564,245	$ 605,253	$ 3,410,728	$ 2,443,066	$ 1,865,045
Expenses
Total results of operations of oil and gas producing activities									23,811	13,093	(1,703)
Company
Expenses
Production costs									191	29	147
Depletion and amortization									17	66	69
Exploration									0	0	0
Abandoned and impaired properties									0	0	0
Results of operations of oil and gas producing activities									(157)	193	(26)
Company's Share of Laramie Energy
Expenses
Production costs									42,706	32,606	27,750
Depletion and amortization									26,819	21,277	17,534
Results of operations of oil and gas producing activities									23,968	12,900	(1,677)
Oil And Gas | Company
Revenue
Revenues									51	288	190
Oil And Gas | Company's Share of Laramie Energy
Revenue
Revenues									$ 93,493	$ 66,783	$ 43,607