Note 5 - Share-based Compensation - Non-vested Stock (Details) - 6 months ended Jun. 30, 2015 - $ / shares	Total
Common Class A [Member]
Outstanding at December 31, 2014 (in shares)	110,647
Outstanding at December 31, 2014 (in dollars per share)	$ 11.10
Granted (in shares)	52,660
Granted (in dollars per share)	$ 13.17
Forfeited (in shares)	(16,249)
Forfeited (in dollars per share)	$ 5.39
Outstanding at June 30, 2015 (in shares)	147,058
Outstanding at June 30, 2015 (in dollars per share)	$ 12.47
Common Class B [Member]
Outstanding at December 31, 2014 (in shares)	18,441
Outstanding at December 31, 2014 (in dollars per share)	$ 36.42
Granted (in shares)	8,776
Granted (in dollars per share)	$ 35.48
Forfeited (in shares)	(2,708)
Forfeited (in dollars per share)	$ 32.31
Outstanding at June 30, 2015 (in shares)	24,509
Outstanding at June 30, 2015 (in dollars per share)	$ 36.54