Note 8 - Earnings Per Share Attributable to Common Shareholder - Potentially Dilutive Securities (Details) - shares	3 Months Ended	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Potentially dilutive securities (in shares)	1,773,734	1,576,949	1,866,127
Service Period Stock Options [Member]
Potentially dilutive securities (in shares)	1,519,431	1,325,836	1,602,279
Restricted Stock Units (RSUs) [Member]
Potentially dilutive securities (in shares)	230,057	220,320	239,602
Performance Shares [Member]
Potentially dilutive securities (in shares)	24,246	30,793	24,246