Income taxes (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Operating loss carry-forward
Current tax expense	$ 1,218	$ 0
Deferred tax assets, valuation allowance	$ 455,300
Effective tax rate (as a percent)	1.00%
Federal | Internal Revenue Service (IRS)
Operating loss carry-forward
Operating loss carryforwards	$ 2,000,000
Operating loss carryforwards subject to expiration	1,700,000
Operating loss carryforwards not subject to expiration	376,200
State | State of Oklahoma
Operating loss carry-forward
Operating loss carryforwards subject to expiration	34,400
State | Texas
Operating loss carry-forward
Net deferred tax assets	$ 0