Note 2 - Securities - Held-to-maturity Securities (Details) - Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member] - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Held-to-maturity securities, amortized cost	$ 27,528	$ 43,099
Held-to-maturity securities, gross unrealized gains	625	836
Held-to-maturity securities, gross unrealized losses	0	0
Held-to-maturity securities, approximate fair value	28,153	43,935
Debt Securities:
Held-to-maturity securities, amortized cost	27,528	43,099
Held-to-maturity securities, gross unrealized gains	625	836
Held-to-maturity securities, gross unrealized losses	0	0
Held-to-maturity securities, approximate fair value	$ 28,153	$ 43,935