Components of income before income taxes from continuing operations (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Tax Disclosure [Abstract]
United States	$ 474,856	$ 398,532	$ 317,655
Foreign	261	(87)	(784)
Income before income taxes	$ 475,117	$ 398,445	$ 316,871