Note 14 - Equity-based Compensation (Tables)

12 Months Ended

Dec. 31, 2019

Notes Tables

Share-based Payment Arrangement, Restricted Stock and Restricted Stock Unit, Activity [Table Text Block]

				Weighted Average
				Grant Date
	Restricted			Fair Value
	Stock			Per Share
Outstanding as of December 31, 2016		38,425		$	402.13
Granted		17,245		$	633.34
Granted due to performance achievement		5,006		$	433.66
Forfeited		(6,223	)	$	469.23
Vested and issued		(3,163	)	$	415.39
Outstanding as of December 31, 2017		51,290		$	472.89
Granted		17,098		$	715.74
Forfeited		(2,455	)	$	636.64
Vested and issued		(25,057	)	$	397.53
Outstanding as of December 31, 2018		40,876		$	610.88
Granted		13,374		$	885.66
Forfeited		(4,111	)	$	710.87
Vested and issued		(11,266	)	$	493.80
Outstanding as of December 31, 2019		38,873		$	728.77
Vested and deferred as of December 31, 2019		5,678		$	527.85

Share-based Payment Arrangement, Stock Appreciation Right, Activity [Table Text Block]

	Stock Appreciation Rights			Weighted Average Exercise Price		Weighted Average Grant Date Fair Value		Aggregate Intrinsic Value (in thousands)		Weighted Average Remaining Contractual Term (in years)
Outstanding as of December 31, 2016		136,000		$	426.80	$	88.07	$	26,510		8.7
Granted		24,432		$	632.15	$	140.44	$	-		9.1
Exercised		(41,603	)	$	424.02	$	87.54	$	11,596		-
Forfeited		(16,371	)	$	422.31	$	87.22
Outstanding as of December 31, 2017		102,458		$	477.62	$	100.91	$	23,173		8.1
Granted		21,000		$	744.47	$	181.21	$	-		8.7
Exercised		(27,060	)	$	435.11	$	90.06	$	9,418		-
Forfeited		(5,793	)	$	502.08	$	108.22
Outstanding as of December 31, 2018		90,605		$	550.60	$	122.29	$	24,673		7.2
Granted		29,000		$	900.90	$	209.57	$	-		8.8
Exercised		(26,092	)	$	491.12	$	105.94	$	20,143		-
Forfeited		(3,103	)	$	659.01	$	154.49
Outstanding as of December 31, 2019		90,410		$	676.41	$	153.90	$	73,419		7.5
Exercisable as of December 31, 2019		35,393		$	489.11	$	104.63	$	35,370		6.1

Schedule of Share-based Payment Award, Other than Options, Valuation Assumptions [Table Text Block]

	2019			2018			2017
Expected volatility		21.69	%		22.22	%		20.83	%
Risk-free interest rate		2.25	%		2.53	%		2.13	%
Expected term (in years)		6.25			6.25			6.25
Expected dividend yield		0.92	%		0.97	%		0.95	%