Segment and Geographical Information - Long Lived Assets and Continuing Operations by Country (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
Revenues From External Customers And Long Lived Assets [Line Items]
Revenues	$ 637,711	$ 524,936
Income (loss) before income taxes	128,309	94,546
Long-lived assets	54,540		$ 57,727
United States [Member]
Revenues From External Customers And Long Lived Assets [Line Items]
Revenues	538,944	443,135
Income (loss) before income taxes	102,782	72,947
Long-lived assets	50,212		53,281
Canada [Member]
Revenues From External Customers And Long Lived Assets [Line Items]
Revenues	98,767	81,801
Income (loss) before income taxes	25,527	$ 21,599
Long-lived assets	$ 4,328		$ 4,446