Income Taxes - Summary of Effective Income Tax Rate Reconciliation (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Tax expense computed at federal statutory rate	$ 96,077	$ 64,048	$ 55,409
State income tax expense, net of federal benefit	17,535	9,810	9,661
Limitation on executive compensation	8,102	4,463	2,912
Rate change effect of tax method changes	0	0	(5,661)
Tax expense (benefit) related to an increase (decrease) in unrecognized tax benefits	473	(1,571)	4,680
Stock based compensation (windfall)/shortfall	(7,907)	(2,828)	415
Federal energy credits	(23,331)	(7,649)	(12,446)
Rate changes	(291)	190	(78)
Change in valuation allowance	(2,128)	121	(885)
Other	1,400	93	(933)
Provision for income taxes	$ 89,930	$ 66,677	$ 53,074
Effective tax rate	19.70%	21.90%	20.10%