Income Taxes (Tables)

3 Months Ended

Mar. 31, 2022

Income Tax Disclosure [Abstract]

Schedule of Effective Income Tax Rate Reconciliation [Table Text Block]

The following table summarizes the differences between our effective tax rate and the federal statutory rate (in thousands):

	Three Months Ended March 31,
	2022				2021
Income before income taxes	$	60,221			$	63,049
Income tax calculated at federal statutory rate	12,646		21.0	%	13,240		21.0	%
Permanent or flow-through adjustments:
State income tax, net of federal provisions	400		0.7		55		0.1
Flow-through repairs deductions	(6,801)		(11.3)		(7,853)		(12.5)
Production tax credits	(3,824)		(6.4)		(4,307)		(6.8)
Amortization of excess deferred income tax	(411)		(0.7)		(265)		(0.4)
Plant and depreciation of flow-through items	(255)		(0.4)		(340)		(0.5)
Share-based compensation	(253)		(0.4)		(261)		(0.4)
Other, net	(391)		(0.7)		(291)		(0.5)
	(11,535)		(19.2)		(13,262)		(21.0)
Income tax expense (benefit)	$	1,111	1.8	%	$	(22)	0.0	%