Federal and State Income Taxes - Summary 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
Current
Federal										$ 47,775	$ 34,461	$ 21,510
State										20,728	14,545	11,960
Total current income tax expense										68,503	49,006	33,470
Deferred
Federal	[1]									(5,396)	(279)	5,372
State	[1]									(1,467)	(77)	1,489
Total deferred income tax (benefit) expense	[1]									(6,863)	(356)	6,861
Total income tax expense		$ 18,950	$ 18,754	$ 14,306	$ 9,630	$ 12,203	$ 12,212	$ 12,568	$ 11,667	61,640	48,650	40,331
Tax benefit of operating loss carryforwards										$ 315	$ 317	$ 443

[1] Includes tax benefit of operating loss carryforwards of $315,000, $317,000 and $443,000 for the years ended December 31, 2020, 2019, and 2018, respectively.