Acquisitions - Pro Forma Information 2018 (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Revenue	$ 1,681,297	$ 1,515,892	$ 1,293,636
Operating income (loss)	$ 496,356	$ 515,040	476,574
OPTIS
Revenue			18,532
Operating income (loss)			$ (5,462)