Income taxes - Allocation of Federal and State Income Taxes between Current and Deferred Portions (Details) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2021	Mar. 31, 2020
Income Tax Disclosure [Abstract]
Current	$ 5,949	$ 8,168
Provision for deferred income taxes	9,639	(8,088)
Total	$ 15,588	$ 80

Amount of deferred income tax expense (benefit) pertaining to income (loss) from continuing operations.

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration