Business Acquisition - Goodwill (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2021	Dec. 31, 2020
Goodwill [Line Items]
Goodwill	$ 1,129,699	$ 914,520
Goodwill, Acquired During Period	210,247
Goodwill, Foreign Currency Translation Gain (Loss)	4,932
Domestic Segment
Goodwill [Line Items]
Goodwill	972,574	854,188
Goodwill, Acquired During Period	118,386
Goodwill, Foreign Currency Translation Gain (Loss)	0
International Segment [Member]
Goodwill [Line Items]
Goodwill	157,125	$ 60,332
Goodwill, Acquired During Period	91,861
Goodwill, Foreign Currency Translation Gain (Loss)	$ 4,932