Note 4 - Investment Securities - Maturities (Details) - USD ($)	Jun. 30, 2016	Dec. 31, 2015
Held-to-Maturity Securities:
Within one year	$ 2,854,000
Within one year	2,877,000
After 1 through 5 years	5,742,000
After 1 through 5 years	5,966,000
After 5 through 10 years	2,077,000
After 5 through 10 years	2,142,000
After 10 years	368,000
After 10 years	387,000
Mortgage-backed securities	1,165,000
Mortgage-backed securities	1,265,000
Held-to-Maturity Securities, Amortized cost	12,206,000	$ 14,371,000
Held-to-Maturity Securities, Fair value	12,637,000	14,910,000
Available-for-Sale Securities:
Within one year	12,245,000
Within one year	12,428,000
After 1 through 5 years	49,308,000
After 1 through 5 years	51,591,000
After 5 through 10 years	170,101,000
After 5 through 10 years	180,119,000
After 10 years	204,993,000
After 10 years	218,493,000
Mortgage-backed securities	395,072,000
Mortgage-backed securities	399,370,000
Available-for-Sale Securities, Amortized cost	831,719,000
Available-for-Sale Securities, Fair value	$ 862,001,000	$ 737,700,000