Components of total lease cost (Details) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2020	Mar. 31, 2019
Lessee Disclosure [Abstract]
Total lease cost		$ 72,740	$ 175,304
Operating lease cost		6,834	8,979
Short-term lease cost	[1]	43,572	134,917
Variable lease cost	[2]	22,334	31,408
Operating cash flows from operating leases		3,046	2,952
Investing cash flows from operating leases		3,980	6,182
Right-of-use assets obtained in exchange for new operating lease liabilities		$ 0	$ 12,191

[1] ⁽¹⁾  Costs associated with short-term lease agreements relate primarily to operational activities where underlying lease terms are less than one year. This amount is significant as it includes drilling and completion activities and field equipment rentals, most of which are contracted for 12 months or less. It is expected that this amount will fluctuate primarily with the number of drilling rigs and completion crews the Company is operating under short-term agreements.

[2] ⁽²⁾  Variable lease payments include additional payments made that were not included in the initial measurement of the ROU asset and corresponding liability for lease agreements with terms longer than 12 months. Variable lease payments relate to the actual volumes transported under certain midstream agreements, actual usage associated with drilling rigs, completion crews, and vehicles, and variable utility costs associated with the Company’s leased office space. Fluctuations in variable lease payments are driven by actual volumes delivered and the number of drilling rigs and completion crews operating under long-term agreements.