Note 15 - Stock-based Compensation - Summary of the Status of the 2012 Incentive Plan (Details) - $ / shares		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Outstanding at beginning of year (in shares)		4.1
Outstanding at beginning of year (in dollars per share)		$ 2,565
Outstanding at end of year (in shares)		4.2	4.1
Outstanding at end of year (in dollars per share)		$ 1,548	$ 2,565
2012 Incentive Plan [Member]
Outstanding at beginning of year (in shares)		2,565,000	2,438,000	4,477,000
Outstanding at beginning of year (in dollars per share)		$ 33.36	$ 25.38	$ 27.48
Stock Options (in shares)		30,000	1,155,000	45,000
Stock Options (in dollars per share)		$ 57.97	$ 43.01	$ 38.24
Exercised (in shares)		(1,181,000)	(967,000)	(1,589,000)
Exercised (in dollars per share)		$ 25.92	$ 25.33	$ 26.77
Forfeited (in shares)		(21,000)	(57,000)	(125,000)
Forfeited (in dollars per share)		$ 46.15	$ 24.12	$ 27.33
Expired (in shares)			(4,000)	(370,000)
Expired (in dollars per share)			$ 26.84	$ 45.78
Outstanding at end of year (in shares)		1,548,000	2,565,000	2,438,000
Outstanding at end of year (in dollars per share)		$ 41.35	$ 33.36	$ 25.38
Options and SARs exercisable at end of year (in shares)		431,000	557,000	858,000
Options and SARs exercisable at end of year (in dollars per share)		$ 32.61	$ 25.22	$ 26.75
Weighted-average fair value of options and SARs granted during the year (in dollars per share)		$ 22.82	$ 11.61	$ 8.68
2012 Incentive Plan [Member] | Stock Appreciation Rights (SARs) [Member]
Other than Options (in shares)	[1]	132,000
Other than Options (in dollars per share)	[1]	$ 62.55
2012 Incentive Plan [Member] | Restricted Stock Units (RSUs) [Member]
Other than Options (in shares)	[2]	23,000
Other than Options (in dollars per share)	[2]

[1] Upon exercise, SARs entitle the recipient to receive shares of common stock with a value 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.