Note 11 - Other Comprehensive Income - Changes in Each Component of Accumulated Other Comprehensive Income (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Balance at Beginning of Period	$ 842,799	$ 738,601
Other comprehensive income (loss)	1,100	(1,238)
Balance at End of Period	873,042	762,496
Accumulated Net Investment Gain (Loss) Attributable to Parent [Member]
Balance at Beginning of Period	(1,955)	1,041
Other comprehensive income before reclassifications	712	3,578
Amounts reclassified from accumulated other comprehensive income	(322)	(374)
Other comprehensive income (loss)	390	3,204
Balance at End of Period	(1,565)	4,245
Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Parent [Member]
Balance at Beginning of Period	(426)	(850)
Other comprehensive income before reclassifications	1,079	(4,442)
Amounts reclassified from accumulated other comprehensive income	(369)
Other comprehensive income (loss)	710	(4,442)
Balance at End of Period	284	(5,292)
AOCI Attributable to Parent [Member]
Balance at Beginning of Period	(2,381)	191
Other comprehensive income before reclassifications	1,791	(864)
Amounts reclassified from accumulated other comprehensive income	(691)	(374)
Other comprehensive income (loss)	1,100	(1,238)
Balance at End of Period	$ (1,281)	$ (1,047)