Income Taxes - Components of Income Tax Expense (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
Income taxes currently payable:
Federal									$ (31,567)	$ 2,051	$ 8,918
State									(5,238)	27	3,241
Aggregate income taxes currently payable									(36,805)	2,078	12,159
Deferred income taxes (benefits):
Federal									(5,903)	5,378	(912)
State									(1,823)	1,706	210
Aggregate deferred income taxes									(7,726)	7,084	(702)
Total income tax expense	$ (11,635)	$ (2,330)	$ (36,328)	$ 5,762	$ 5,854	$ 782	$ 5,735	$ (3,209)	$ (44,531)	$ 9,162	$ 11,457