Income taxes (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Sep. 30, 2020	Sep. 30, 2019
Operating Loss Carryforwards [Line Items]
CARES Act, reduction in tax payments			$ 5,000
Income tax payments			$ 39,872	$ 73,457
Federal
Operating Loss Carryforwards [Line Items]
Income tax payments		$ 30,000
Federal | Forecast
Operating Loss Carryforwards [Line Items]
Income tax payments	$ 40,000