Note 7 - Stock-based Compensation - RSU Summary (Details) - $ / shares		12 Months Ended
		Dec. 31, 2023	Dec. 31, 2022		Dec. 31, 2021
Balance (in shares)		2,659,000	2,509,000		3,105,000
Weighted-Average Grant Date Fair Value Per Share, ending balance (in dollars per share)		$ 176.5	$ 136.87		$ 87.42
Granted (in shares)		363,000	1,001,000		411,000
Weighted-Average Grant Date Fair Value Per Share, granted (in dollars per share)		$ 444.86	$ 215.63		$ 357.49
Vested (in shares)		(911,000)	(837,000)		(972,000)
Weighted-Average Grant Date Fair Value Per Share, vested (in dollars per share)		$ 177.54	$ 103.02		$ 72.69
Forfeited (in shares)		(25,000)	(14,000)		(35,000)
Weighted-Average Grant Date Fair Value Per Share, forfeited (in dollars per share)		$ 209.23	$ 275.47		$ 124.5
Balance (in shares)		2,086,000	2,659,000		2,509,000
Weighted-Average Grant Date Fair Value Per Share, ending balance (in dollars per share)		$ 222.04	$ 176.5		$ 136.87
Time-Based RSUs [Member]
Balance (in shares)		106,000	125,000		161,000
Weighted-Average Grant Date Fair Value Per Share, ending balance (in dollars per share)		$ 327.13	$ 235.82		$ 151.62
Granted (in shares)		51,000	49,000		46,000
Weighted-Average Grant Date Fair Value Per Share, granted (in dollars per share)		$ 472.38	$ 390.89		$ 384.33
Vested (in shares)		(49,000)	(61,000)		(71,000)
Weighted-Average Grant Date Fair Value Per Share, vested (in dollars per share)		$ 296.65	$ 193.18		$ 144.46
Forfeited (in shares)		(6,000)	(7,000)		(11,000)
Weighted-Average Grant Date Fair Value Per Share, forfeited (in dollars per share)		$ 387.61	$ 316		$ 207.04
Balance (in shares)		102,000	106,000		125,000
Weighted-Average Grant Date Fair Value Per Share, ending balance (in dollars per share)		$ 411.11	$ 327.13		$ 235.82
PSUs and MPSUs [Member]
Balance (in shares)		748,000	1,166,000		1,390,000
Weighted-Average Grant Date Fair Value Per Share, ending balance (in dollars per share)		$ 275.7	$ 222.78		$ 132.6
Granted (in shares)	[1]	281,000	35,000	[2]	365,000
Weighted-Average Grant Date Fair Value Per Share, granted (in dollars per share)		$ 449.38	$ 385.8		$ 354.12
Vested (in shares)		(543,000)	(452,000)		(577,000)
Weighted-Average Grant Date Fair Value Per Share, vested (in dollars per share)		$ 257.24	$ 147.78		$ 91.5
Forfeited (in shares)		(4,000)	(1,000)		(12,000)
Weighted-Average Grant Date Fair Value Per Share, forfeited (in dollars per share)		$ 315.19	$ 377.86		$ 103.84
Balance (in shares)		482,000	748,000		1,166,000
Weighted-Average Grant Date Fair Value Per Share, ending balance (in dollars per share)		$ 397.77	$ 275.7		$ 222.78
MSUs [Member]
Balance (in shares)		1,805,000	1,218,000		1,554,000
Weighted-Average Grant Date Fair Value Per Share, ending balance (in dollars per share)		$ 126.57	$ 44.59		$ 40.4
Granted (in shares)		31,000	917,000		0
Weighted-Average Grant Date Fair Value Per Share, granted (in dollars per share)		$ 330.95	$ 199.63		$ 0
Vested (in shares)		(319,000)	(324,000)		(324,000)
Weighted-Average Grant Date Fair Value Per Share, vested (in dollars per share)		$ 23.57	$ 23.57		$ 23.57
Forfeited (in shares)		(15,000)	(6,000)		(12,000)
Weighted-Average Grant Date Fair Value Per Share, forfeited (in dollars per share)		$ 110.65	$ 216.37		$ 68.48
Balance (in shares)		1,502,000	1,805,000		1,218,000
Weighted-Average Grant Date Fair Value Per Share, ending balance (in dollars per share)		$ 152.89	$ 126.57		$ 44.59

[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.

[2] Amount included grants and cancellations of the 2022 Executive PSUs as defined under the "2022 PSUs" section.