Goodwill and Other Intangible Assets - Goodwill Roll Forward (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
Goodwill [Roll Forward]
Balance, beginning of year	$ 898,569	$ 808,322
Goodwill acquired during the year	0	92,844
Purchase accounting adjustments	2,743	(2,732)
Balance, end of year	901,312	898,434
Accumulated impairment losses at end of year	$ 0	$ 0