Income taxes - Schedule of Allocation of Federal and State Income Taxes between Current and Deferred Portions (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Income Tax Disclosure [Abstract]
Current	$ 6,546	$ 2,195	$ 16,740	$ 2,195
Deferred	(232)	5,599	(4,451)	11,081
Total	$ 6,314	$ 7,794	$ 12,289	$ 13,276

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

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Data Type:	xbrli:monetaryItemType
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