Components of total lease cost (Details) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Lessee Disclosure [Abstract]
Total lease cost		$ 62,219	$ 139,762	$ 134,959	$ 315,066
Operating lease cost		4,453	11,479	11,287	20,458
Short-term lease cost	[1]	36,630	102,085	80,202	237,002
Variable lease cost	[2]	21,136	26,198	43,470	57,606
Operating cash flows from operating leases				6,065	5,966
Investing cash flows from operating leases				6,188	14,808
Right-of-use assets obtained in exchange for new operating lease liabilities		$ 745	$ 10,500	$ 745	$ 22,700

[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.