Income Tax - Components of Income Tax Expense (Benefit) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Currently Payable:
Federal									$ 28,463	$ 23,938	$ 23,633
State									2,647	422	1,842
Deferred:
Federal									(8,508)	4,726	6,723
State									(1,227)	239	(3,199)
Income Tax Expense	$ 7,641	$ 5,621	$ 4,623	$ 3,490	$ 8,298	$ 6,337	$ 7,749	$ 6,941	$ 21,375	$ 29,325	$ 28,999