Income Taxes - Provision for Income Taxes (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Income Tax Disclosure [Abstract]
Income taxes currently payable	$ 19,329	$ 17,282	$ 51,000	$ 40,356
Deferred income taxes	(1,696)	5,993	2,920	10,933
Actual tax provision	$ 17,633	$ 23,275	$ 53,920	$ 51,289