Goodwill and Other Intangible Assets - Goodwill Roll Forward (Details) - USD ($)	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
Goodwill [Roll Forward]
Balance, beginning of year	$ 808,322,000	$ 808,726,000
Goodwill acquired during the year	92,844,000	0
Purchase accounting adjustments	0	(404,000)
Impairment losses	0	0
Balance, end of year	901,166,000	808,322,000
Accumulated impairment losses at end of year	$ 0	$ 0