Note 10 - Fair Value of Financial Instruments - Fair Value Measured on a Recurring Basis (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Assets	$ 843,353	$ 867,731
Liabilities	39,761	37,345
Fair Value, Inputs, Level 1 [Member]
Assets
Liabilities
Fair Value, Inputs, Level 2 [Member]
Assets	835,909	860,370
Liabilities	4,624	3,386
Fair Value, Inputs, Level 3 [Member]
Assets	7,444	7,361
Liabilities	35,137	33,959
Collateralized Mortgage Backed Securities [Member]
Assets	520,012	516,476
Collateralized Mortgage Backed Securities [Member] | Fair Value, Inputs, Level 1 [Member]
Assets
Collateralized Mortgage Backed Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Assets	520,012	516,476
Collateralized Mortgage Backed Securities [Member] | Fair Value, Inputs, Level 3 [Member]
Assets
Other Securities [Member]
Assets	317,693	344,905
Other Securities [Member] | Fair Value, Inputs, Level 1 [Member]
Assets
Other Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Assets	310,249	337,544
Other Securities [Member] | Fair Value, Inputs, Level 3 [Member]
Assets	7,444	7,361
Interest Rate Swap [Member]
Assets	5,648	6,350
Liabilities	4,624	3,386
Interest Rate Swap [Member] | Fair Value, Inputs, Level 1 [Member]
Assets
Liabilities
Interest Rate Swap [Member] | Fair Value, Inputs, Level 2 [Member]
Assets	5,648	6,350
Liabilities	4,624	3,386
Interest Rate Swap [Member] | Fair Value, Inputs, Level 3 [Member]
Assets
Liabilities
Junior Subordinated Debentures [Member]
Liabilities	35,137	33,959
Junior Subordinated Debentures [Member] | Fair Value, Inputs, Level 1 [Member]
Liabilities
Junior Subordinated Debentures [Member] | Fair Value, Inputs, Level 2 [Member]
Liabilities
Junior Subordinated Debentures [Member] | Fair Value, Inputs, Level 3 [Member]
Liabilities	$ 35,137	$ 33,959