Note 3 - Stock-based Compensation - RSU Summary (Details)	6 Months Ended
	Jun. 30, 2023 $ / shares shares
Balance (in shares) | shares	2,659,000
Weighted-Average Grant Date Fair Value Per Share, ending balance (in dollars per share) | $ / shares	$ 176.50
Granted (in shares) | shares	268,000
Weighted-Average Grant Date Fair Value Per Share, granted (in dollars per share) | $ / shares	$ 450.48
Vested (in shares) | shares	(495,000)
Weighted-Average Grant Date Fair Value Per Share, vested (in dollars per share) | $ / shares	$ 204.90
Forfeited (in shares) | shares	(10,000)
Weighted-Average Grant Date Fair Value Per Share, forfeited (in dollars per share) | $ / shares	$ 236.17
Balance (in shares) | shares	2,422,000
Weighted-Average Grant Date Fair Value Per Share, ending balance (in dollars per share) | $ / shares	$ 201.23
Time-Based RSUs [Member]
Balance (in shares) | shares	106,000
Weighted-Average Grant Date Fair Value Per Share, ending balance (in dollars per share) | $ / shares	$ 327.13
Granted (in shares) | shares	38,000
Weighted-Average Grant Date Fair Value Per Share, granted (in dollars per share) | $ / shares	$ 467.77
Vested (in shares) | shares	(35,000)
Weighted-Average Grant Date Fair Value Per Share, vested (in dollars per share) | $ / shares	$ 277.81
Forfeited (in shares) | shares	(3,000)
Weighted-Average Grant Date Fair Value Per Share, forfeited (in dollars per share) | $ / shares	$ 365.67
Balance (in shares) | shares	106,000
Weighted-Average Grant Date Fair Value Per Share, ending balance (in dollars per share) | $ / shares	$ 392.85
PSUs and MPSUs [Member]
Balance (in shares) | shares	748,000
Weighted-Average Grant Date Fair Value Per Share, ending balance (in dollars per share) | $ / shares	$ 275.70
Granted (in shares) | shares	230,000	[1]
Weighted-Average Grant Date Fair Value Per Share, granted (in dollars per share) | $ / shares	$ 449.23
Vested (in shares) | shares	(298,000)
Weighted-Average Grant Date Fair Value Per Share, vested (in dollars per share) | $ / shares	$ 294.82
Forfeited (in shares) | shares	(2,000)
Weighted-Average Grant Date Fair Value Per Share, forfeited (in dollars per share) | $ / shares	$ 287.76
Balance (in shares) | shares	678,000
Weighted-Average Grant Date Fair Value Per Share, ending balance (in dollars per share) | $ / shares	$ 327.00
MSUs [Member]
Balance (in shares) | shares	1,805,000
Weighted-Average Grant Date Fair Value Per Share, ending balance (in dollars per share) | $ / shares	$ 126.57
Granted (in shares) | shares	0
Weighted-Average Grant Date Fair Value Per Share, granted (in dollars per share) | $ / shares	$ 0
Vested (in shares) | shares	(162,000)
Weighted-Average Grant Date Fair Value Per Share, vested (in dollars per share) | $ / shares	$ 23.57
Forfeited (in shares) | shares	(5,000)
Weighted-Average Grant Date Fair Value Per Share, forfeited (in dollars per share) | $ / shares	$ 139.15
Balance (in shares) | shares	1,638,000
Weighted-Average Grant Date Fair Value Per Share, ending balance (in dollars per share) | $ / shares	$ 136.72

[1] Amount reflects the number of awards that may ultimately be earned based on management's probability assessment of the achievement of performance conditions at each reporting period.