Note 5 - Share-based Compensation - Stock Option Activity (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2015
Common Class A [Member]
Outstanding, number of options (in shares)	1,324,520
Outstanding, weighted average exercise price (in dollars per share)	$ 11.07
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross	81,306
Granted, weighted average exercise price (in dollars per share)	$ 13.17
Exercised, number of options (in shares)	(25,983)
Exercised, weighted average exercise price (in dollars per share)	$ 6.30
Exercised, aggregate intrinsic value	$ 178
Forfeited, number of options (in shares)	(56,105)
Forfeited, weighted average exercise price (in dollars per share)	$ 13.12
Outstanding, number of options (in shares)	1,323,738
Outstanding, weighted average exercise price (in dollars per share)	$ 11.21
Outstanding, weighted average remaining contractual term (years)	6 years 80 days
Outstanding, aggregate intrinsic value	4,740
Exercisable, number of options (in shares)	879,990
Exercisable, weighted average exercise price (in dollars per share)	$ 10.24
Exercisable, weighted average remaining contractual term (years)	5 years 91 days
Exercisable, aggregate intrinsic value	4,019
Exercised, number of options (in shares)	(25,983)
Forfeited, number of options (in shares)	(56,105)
Outstanding, aggregate intrinsic value	4,740
Common Class B [Member]
Outstanding, number of options (in shares)	213,470
Outstanding, weighted average exercise price (in dollars per share)	$ 24.32
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross	13,551
Granted, weighted average exercise price (in dollars per share)	$ 35.48
Exercised, number of options (in shares)	(4,330)
Exercised, weighted average exercise price (in dollars per share)	$ 14.82
Exercised, aggregate intrinsic value	89
Forfeited, number of options (in shares)	(9,018)
Forfeited, weighted average exercise price (in dollars per share)	$ 27.61
Outstanding, number of options (in shares)	213,673
Outstanding, weighted average exercise price (in dollars per share)	$ 25.09
Outstanding, weighted average remaining contractual term (years)	6 years 98 days
Outstanding, aggregate intrinsic value	1,821
Exercisable, number of options (in shares)	140,663
Exercisable, weighted average exercise price (in dollars per share)	$ 20.89
Exercisable, weighted average remaining contractual term (years)	5 years 109 days
Exercisable, aggregate intrinsic value	1,517
Exercised, number of options (in shares)	(4,330)
Forfeited, number of options (in shares)	(9,018)
Outstanding, aggregate intrinsic value	$ 1,821