Income Taxes - Reconciliation (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Taxes
Statutory tax rate (as a percent)									21.00%	21.00%	35.00%
Computed at the statutory rate (21% for 2019 and 2018, and 35% for 2017)									$ 21,448	$ 17,646	$ 27,006
Increase resulting from
State income taxes									2,989	4,944	2,399
Effect of Tax Cuts and Jobs Act											(6,928)
Tax Credits net of related amortization									(190)	(1,533)
Other									558	96
Income tax expense	$ 9,434	$ 6,502	$ 5,328	$ 3,541	$ 5,699	$ 5,584	$ 5,186	$ 4,684	$ 24,805	$ 21,153	$ 22,477