Goodwill and Other Intangible Assets - Goodwill Roll Forward (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Goodwill [Roll Forward]
Balance, beginning of year	$ 808,322	$ 808,726	$ 493,329
Goodwill acquired during the year	92,844	0	313,043
Purchase accounting adjustments	(2,597)	(404)	2,354
Balance, end of year	898,569	808,322	808,726
Accumulated impairment losses at end of year	$ 0	$ 0	$ 0