Note 7 - Share-based Compensation - Stock-settled Stock Appreciation Rights Transactions (Details) - Stock Appreciation Rights (SARs) [Member] - USD ($)		3 Months Ended	12 Months Ended
		Mar. 31, 2020	Dec. 31, 2019
Outstanding SARS (in shares)		206,700
Outstanding SARS, weighted average exercise price (in dollars per share)		$ 18.67
Outstanding SARS, weighted average remaining life (Year)		3 years 149 days	2 years 14 days
Outstanding SARS, aggregate intrinsic value
Granted SARs (in shares)	[1]	153,822
Granted SARS, weighted average exercise price (in dollars per share)	[1]	$ 10.97
Exercised SARs (in shares)
Exercised SARS, weighted average exercise price (in dollars per share)
Lapsed or cancelled (in shares)		(68,501)
Lapsed or cancelled, weighted average exercise price (in dollars per share)		$ 15.97
Outstanding SARS (in shares)		292,021	206,700
Outstanding SARS, weighted average exercise price (in dollars per share)		$ 15.25	$ 18.67
Exercisable (in shares)		126,068
Exercisable, weighted average exercise price (in dollars per share)		$ 18.95
Exercisable, weighted average remaining life (Year)		1 year 302 days
Exercisable, aggregate intrinsic value

[1] The weighted average grant date fair value of SARs granted was $2.14 per share.