Note 15 - Stock-based Compensation - Summary of the Status of the Incentive Plan (Details) - $ / shares						1 Months Ended	12 Months Ended
	Dec. 31, 2020	Nov. 03, 2020	Jul. 01, 2020	Jun. 15, 2020	May 12, 2020	Nov. 30, 2021	Dec. 31, 2021		Dec. 31, 2020		Dec. 31, 2019
Outstanding at beginning of year (in shares)							2,240,000
Outstanding at end of year (in shares)	2,240,000						2,025,000		2,240,000
The 2018 Incentive Plan [Member]
Outstanding at beginning of year (in shares)							2,240,000		1,792,000		2,527,000
Outstanding, weighted average exercise price (in dollars per share)							$ 57.68		$ 50.39		$ 46.77
Exercised (in shares)							(159,000)		(469,000)		(711,000)
Exercised, weighted average exercise price (in dollars per share)							$ 40.47		$ 45.71		$ 37.83
Forfeited (in shares)							(83,000)		(100,000)		(71,000)
Forfeited, weighted average exercise price (in dollars per share)							$ 64.34		$ 55.05		$ 50.59
Expired (in shares)							0		0		0
Expired, weighted average exercise price (in dollars per share)							$ 0		$ 0		$ 0
Outstanding at end of year (in shares)	2,240,000						2,025,000		2,240,000		1,792,000
Outstanding, weighted average exercise price (in dollars per share)	$ 57.68						$ 58.70		$ 57.68		$ 50.39
Options and SARs exercisable at end of year (in shares)	704,000						881,000		704,000		479,000
Options and SARs exercisable at end of year, weighted average exercise price (in dollars per share)	$ 51.64						$ 53.20		$ 51.64		$ 48.35
Weighted-average fair value of awards granted during the year, weighted average exercise price (in dollars per share)	$ 20.84						$ 46.23		$ 20.84		$ 29.24
The 2018 Incentive Plan [Member] | Stock Appreciation Rights (SARs) [Member]
Other than Options (in shares)	573		45,365	852,475	46,795		15,000	[1]	957,000	[1]	38,000	[1]
Other than Options, weighted average exercise price (in dollars per share)	$ 25.50	$ 18.25	$ 16.5	$ 18.0	$ 17.6		$ 77.22	[1]	$ 68.82	[1]	$ 69.13	[1]
The 2018 Incentive Plan [Member] | Restricted Stock Units (RSUs) [Member]
Other than Options (in shares)	2,103		6,020	11,068	6,142		12,000	[2]	35,000	[2]	9,000	[2]
Other than Options, weighted average exercise price (in dollars per share)	$ 89.15	$ 67.13	$ 62.3	$ 68.0	$ 67.2	$ 76.2	$ 0	[2]	$ 0	[2]	$ 0	[2]
The 2018 Incentive Plan [Member] | Performance Stock Units (PSU) [Member]
Other than Options (in shares)	1,952		6,540	10,962	5,637		0	[3]	25,000	[3]	0	[3]
Other than Options, weighted average exercise price (in dollars per share)	$ 96.10		$ 57.3	$ 65.0	$ 73.2		$ 0	[3]	$ 0	[3]	$ 0	[3]

[1] Upon exercise, SARs entitle the recipient to receive shares of common stock equal to the increase in value of the award between the grant date and the exercise date.

[2] An RSU represents the right to receive one share of common stock once certain vesting conditions are met. The value of an RSU is identical to the value of the underlying stock.

[3] The Performance shares units shall be paid out based on achievement of three-year relative total stockholder return compared to other companies in S&P 500 index.