Note 8 - Stock-based Compensation - Summary of Restricted Common Stock Activity (Details) - $ / shares	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Restricted Stock [Member]
Outstanding, Shares (in shares)	1,035,728	917,533	977,547
Outstanding, Weighted average grant date fair value (in dollars per share)	$ 19.69	$ 16.84	$ 15.45
Granted, Shares (in shares)	400,927	731,374	359,481
Granted, Weighted average grant date fair value (in dollars per share)	$ 21.68	$ 19.73	$ 18.92
Vested, Shares (in shares)	(438,910)	(613,179)	(333,865)
Vested, Weighted average grant date fair value (in dollars per share)	$ 19.38	$ 15.48	$ 15.35
Forfeited, Shares (in shares)	0	0	(85,630)
Forfeited, Weighted average grant date fair value (in dollars per share)	$ 0	$ 0	$ 15.53
Outstanding, Shares (in shares)	997,745	1,035,728	917,533
Outstanding, Weighted average grant date fair value (in dollars per share)	$ 20.62	$ 19.69	$ 16.84
Restricted Stock [Member] | Common Class A [Member]
Outstanding, Shares (in shares)	720,421	480,042	449,284
Outstanding, Weighted average grant date fair value (in dollars per share)	$ 18.22	$ 16.10	$ 13.55
Granted, Shares (in shares)	250,448	488,918	166,814
Granted, Weighted average grant date fair value (in dollars per share)	$ 20.52	$ 18.66	$ 19.87
Vested, Shares (in shares)	(293,631)	(248,539)	(136,056)
Vested, Weighted average grant date fair value (in dollars per share)	$ 17.55	$ 15.00	$ 12.32
Outstanding, Shares (in shares)	677,238	720,421	480,042
Outstanding, Weighted average grant date fair value (in dollars per share)	$ 19.36	$ 18.22	$ 16.10
Restricted Stock Units (RSUs) [Member]
Outstanding, Shares (in shares)	125,247	90,184	398,000
Outstanding, Weighted average grant date fair value (in dollars per share)	$ 19.02	$ 18.92	$ 18.21
Granted, Shares (in shares)	259,079	95,115	93,184
Granted, Weighted average grant date fair value (in dollars per share)	$ 23.87	$ 19.05	$ 18.77
Vested, Shares (in shares)	(108,921)	(60,052)	(374,500)
Vested, Weighted average grant date fair value (in dollars per share)	$ 19.03	$ 18.92	$ 18.18
Forfeited, Shares (in shares)	(1,260)	0	(26,500)
Forfeited, Weighted average grant date fair value (in dollars per share)	$ 19.05	$ 0	$ 18.21
Outstanding, Shares (in shares)	274,145	125,247	90,184
Outstanding, Weighted average grant date fair value (in dollars per share)	$ 23.60	$ 19.02	$ 18.92