Note 12 - Stock Incentive Plans (Details Textual) - shares shares in Millions			9 Months Ended
	Jul. 24, 2020	Jun. 16, 2020	Sep. 30, 2020
Amended 2012 ESPP [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Number of Additional Shares Authorized (in shares)	0.6	0.6
Restricted Stock Units (RSUs) [Member] | Share-based Compensation Award, Issued in 2020 [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period (Year)			3 years
Performance Share Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period (Year)			3 years
Performance Share Units [Member] | Share-based Compensation Awards Issued in 2019, Vesting Period [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period (Year)			3 years