Note 12 - Compensation Plans - Summary of Stock Activity (Details) - USD ($) $ / shares in Units, $ in Millions		6 Months Ended	18 Months Ended
		Jun. 30, 2023	Jun. 30, 2023	Dec. 31, 2022
Outstanding beginning balance, options (in shares)		4,023,816
Outstanding beginning balance, options, weighted average exercise price (in dollars per share)		$ 132.90
Outstanding, options, aggregate intrinsic value		$ 252.9	$ 252.9	$ 193.3
Granted, options (in shares)		205,351
Granted, options, weighted average exercise price (in dollars per share)		$ 183.97
Dividend reinvestment, options (in shares)		0
Dividend reinvestment, options, weighted average exercise price (in (in dollars per share)		$ 0
Exercised or lapsed, options (in shares)		(1,049,105)
Exercised or lapsed, options, weighted average exercise price (in dollars per share)		$ 108.83
Exercised or lapsed, options, aggregate intrinsic value			$ 86.7
Canceled, expired or forfeited, option (in shares)		(197,034)
Canceled, expired or forfeited, options, weighted average exercise price (in dollars per share)		$ 187.69
Outstanding, option (in shares)		2,983,028	2,983,028
Outstanding beginning balance, options, weighted average exercise price (in dollars per share)		$ 141.26	$ 141.26
Exercisable, options (in shares)		2,208,396	2,208,396	2,702,075
Exercisable, options, weighted average exercise price (in dollars per share)		$ 125.45	$ 125.45	$ 110.02
Exercisable, options, aggregate intrinsic value		$ 222.2	$ 222.2	$ 182.6
Nonvested, options (in shares)		774,632	774,632
Expected to vest, options (in shares)		687,630	687,630
Restricted Stock [Member]
Outstanding beginning balance, number of shares (in shares)		307,575
Outstanding beginning balance, weighted average exercise price (in dollars per share)		$ 182.07
Granted, number of shares (in shares)		192,836
Granted, weighted average exercise price (in dollars per share)		$ 184.94
Dividend reinvestment, number of shares (in shares)		0
Dividend reinvestment (in dollars per share)		$ 0
Exercised or lapsed, number of shares (in shares)		(162,662)
Exercised or lapsed, weighted average exercise price (in dollars per share)		$ 179.02
Canceled, expired or forfeited, number of shares (in shares)		(20,616)
Canceled, expired or forfeited, weighted average exercise price (in dollars per share)		$ 181.58
Outstanding ending balance, number of shares (in shares)		317,133	317,133
Outstanding ending balance, weighted average exercise price (in dollars per share)		$ 185.93	$ 185.93
Nonvested, number of shares (in shares)		317,133	317,133	307,575
Expected, number of shares (in shares)		276,302	276,302
Performance Shares [Member]
Outstanding beginning balance, number of shares (in shares)		199,494
Outstanding beginning balance, weighted average exercise price (in dollars per share)		$ 195.34
Granted, number of shares (in shares)		48,486
Granted, weighted average exercise price (in dollars per share)		$ 212.86
Dividend reinvestment, number of shares (in shares)		625
Exercised or lapsed, number of shares (in shares)		(45,997)
Canceled, expired or forfeited, number of shares (in shares)		(18,487)
Canceled, expired or forfeited, weighted average exercise price (in dollars per share)		$ 205.58
Outstanding ending balance, number of shares (in shares)		184,121	184,121
Outstanding ending balance, weighted average exercise price (in dollars per share)		$ 199.70	$ 199.70
Nonvested, number of shares (in shares)		184,121	184,121	199,494
Expected, number of shares (in shares)	[1]	216,330	216,330

[1] Includes estimated performance achievement