Note 6 - Share-based Compensation (Tables)

12 Months Ended

Dec. 31, 2021

Notes Tables

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

	Years ended December 31,
	2021		2020		2019
Restricted share units
Pretax compensation expense	$	44,505	$	47,044	$	38,632
Tax benefit		10,637		11,300		9,337
Restricted share units, net of tax	$	33,868	$	35,744	$	29,295
Performance share units
Pretax compensation expense	$	17,000	$	13,654	$	14,692
Tax benefit		4,063		3,280		3,551
Performance share awards, net of tax	$	12,937	$	10,374	$	11,141

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, 2018		1,245,835		$	86.80
Granted		440,255			99.60
Vested		(341,218	)		85.61
Forfeited		(31,454	)		93.91
Unvested at December 31, 2019		1,313,418		$	91.22
Granted		511,859			110.49
Vested		(457,437	)		93.78
Forfeited		(22,694	)		102.03
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

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, 2018		360,512		$	93.74
Granted		142,156			98.58
Vested		(127,140	)		93.46
Forfeited		-			-
Unvested at December 31, 2019		375,528		$	95.67
Granted		202,023			112.87
Vested		(145,038	)		89.75
Forfeited		(98,588	)		110.19
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