Note 9 - Phantom Stock Plan (Details) - Phantom Share Units (PSUs) [Member] - Phantom Stock Plan [Member]	3 Months Ended
	Jun. 30, 2016 $ / shares shares
Outstanding at December 31, 2015 (in shares) | shares	79,440
Outstanding at December 31, 2015 (in dollars per share) | $ / shares	$ 21.64
Granted (in shares) | shares	10,905
Granted (in dollars per share) | $ / shares	$ 19.88
Forfeited (in shares) | shares
Forfeited (in dollars per share) | $ / shares
Distributions (in shares) | shares	(1,363)
Distributions (in dollars per share) | $ / shares	$ 20.28
Outstanding at June 30, 2016 (in shares) | shares	88,982
Outstanding at June 30, 2016 (in dollars per share) | $ / shares	$ 19.88
Vested at June 30, 2016 (in shares) | shares	88,667
Vested at June 30, 2016 (in dollars per share) | $ / shares	$ 19.88