Goodwill and Other Intangible Assets - Goodwill Roll Forward (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2020	Sep. 30, 2019
Goodwill [Roll Forward]
Balance, beginning of year	$ 898,434	$ 808,322	$ 808,726
Goodwill acquired during the year		92,844	0
Purchase accounting adjustments		(2,732)	(404)
Balance, end of year	898,434	898,434	808,322
Accumulated impairment losses at end of year	$ 0	$ 0	$ 0