Note 7 - Loans - Aging of Troubled Debt Restructurings (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Loans current and past due less than 30 days	$ 1,126,154	$ 810,195
Nonaccrual loans	9,020	13,113
Financial Asset, Equal to or Greater than 90 Days Past Due [Member]
Loans past due	6,538	9,060
Troubled Debt Restructuring [Member]
Loans current and past due less than 30 days	716	612
Loans past due	73	0
Nonaccrual loans	1,671	2,884
Troubled debt restructurings	2,668	3,539
Troubled Debt Restructuring [Member] | Financial Asset, Equal to or Greater than 90 Days Past Due [Member]
Loans past due	$ 208	$ 43