Note 7 - Stock-based Compensation (Details Textual) - USD ($) $ / shares in Units, $ in Millions | 9 Months Ended |
Sep. 30, 2015 | Sep. 30, 2014 |
Restricted Stock [Member] | January 31, 2017 [Member] | Employee [Member] | Common Class A [Member] | | |
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding, Number | 76,442 | |
Restricted Stock [Member] | January 31, 2017 [Member] | Employee [Member] | | |
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding, Number | 50,100 | |
Restricted Stock [Member] | January 31, 2016 [Member] | Employee [Member] | Common Class A [Member] | | |
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding, Number | 76,442 | |
Restricted Stock [Member] | January 31, 2016 [Member] | Employee [Member] | | |
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding, Number | 50,102 | |
Restricted Stock [Member] | January 31, 2016 [Member] | Common Class A [Member] | Director [Member] | | |
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding, Number | 58,191 | |
Restricted Stock [Member] | January 17, 2017 [Member] | Employee [Member] | Common Class A [Member] | | |
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding, Number | | 43,590 |
Restricted Stock [Member] | January 17, 2017 [Member] | Employee [Member] | | |
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding, Number | | 58,327 |
Restricted Stock [Member] | January 1, 2015 [Member] | Common Class A [Member] | Director [Member] | | |
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding, Number | | 41,881 |
Restricted Stock [Member] | January 31, 2018 [Member] | Employee [Member] | Common Class A [Member] | | |
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding, Number | 76,438 | |
Restricted Stock [Member] | January 31, 2018 [Member] | Employee [Member] | | |
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding, Number | 50,106 | |
Restricted Stock [Member] | January 17, 2015 [Member] | Employee [Member] | Common Class A [Member] | | |
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding, Number | | 75,412 |
Restricted Stock [Member] | January 17, 2015 [Member] | Employee [Member] | | |
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding, Number | | 127,316 |
Restricted Stock [Member] | January 17, 2016 [Member] | Employee [Member] | Common Class A [Member] | | |
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding, Number | | 43,590 |
Restricted Stock [Member] | January 17, 2016 [Member] | Employee [Member] | | |
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding, Number | | 58,327 |
Restricted Stock [Member] | Employee [Member] | Common Class A [Member] | | |
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding, Number | | 31,821 |
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period | 229,322 | 194,413 |
Restricted Stock [Member] | Employee [Member] | | |
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period | 150,308 | 312,961 |
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period | | 68,991 |
Restricted Stock [Member] | Common Class A [Member] | Director [Member] | | |
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period | 58,191 | 41,881 |
Restricted Stock [Member] | Common Class A [Member] | | |
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period | 287,513 | 236,294 |
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period | 117,293 | 31,821 |
Restricted Stock [Member] | Directors Restricted Stock Plan [Member] | | |
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period | 0 | 0 |
Restricted Stock [Member] | | |
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period | 150,308 | 312,961 |
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period | 197,858 | 202,743 |
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number | 274,746 | 274,746 |
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price | $ 1.99 | $ 1.99 |
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Number | 206,064 | 137,376 |
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Intrinsic Value | $ 3 | |