Note 5 - Share-based Compensation (Tables)

12 Months Ended

Dec. 31, 2023

Notes Tables

Share-Based Payment Arrangement, Expensed and Capitalized, Amount [Table Text Block]

	Years ended December 31,
	2023		2022		2021
Restricted share units
Pretax compensation expense	$	56,837	$	54,276	$	44,505
Tax benefit		12,561		13,216		10,637
Restricted share units, net of tax	$	44,276	$	41,060	$	33,868
Performance share units
Pretax compensation expense	$	22,352	$	23,259	$	17,000
Tax benefit		4,940		5,664		4,063
Performance share awards, net of tax	$	17,412	$	17,595	$	12,937

Schedule of Nonvested Restricted Stock Units Activity [Table Text Block]

Restricted Share Units	Number of Shares			Weighted Average Grant Date Fair Value
Unvested at December 31, 2020		1,345,146		$	97.22
Granted		360,734			150.33
Vested		(387,948	)		100.36
Forfeited		(27,700	)		118.20
Unvested at December 31, 2021		1,290,232		$	110.83
Granted		317,751			189.66
Vested		(427,942	)		118.00
Forfeited		(38,704	)		138.94
Unvested at December 31, 2022		1,141,337		$	129.75
Granted		277,234			180.00
Vested		(443,883	)		125.36
Forfeited		(38,196	)		143.45
Unvested at December 31, 2023		936,492		$	147.02

Schedule of Nonvested Performance-Based Units Activity [Table Text Block]

Performance Share Units	Number of Shares			Weighted Average Grant Date Fair Value
Unvested at December 31, 2020		333,925		$	109.57
Granted		135,500			143.32
Vested		(95,415	)		103.21
Forfeited		-			-
Unvested at December 31, 2021		374,010		$	123.42
Granted		135,842			189.05
Vested		(108,823	)		117.57
Forfeited		-			-
Unvested at December 31, 2022		401,029		$	146.96
Granted		150,051			174.23
Vested		(142,346	)		127.36
Forfeited		(22,011	)		170.87
Unvested at December 31, 2023		386,723		$	163.87