Note 2 - Investment Securities - Investment Securities Available for Sale (Details) $ in Thousands	Mar. 31, 2017 USD ($)
Number of investment positions - less than twelve months	166
Fair value - less than twelve months	$ 204,268
Gross unrealized losses - less than twelve months	$ 3,760
Number of investment positions - more than twelve months	8
Fair value - more than twelve months	$ 9,333
Gross unrealized losses - more than twelve months	$ 122
Number of investment positions	174
Fair value	$ 213,601
Gross unrealized losses	$ 3,882
US Government Agencies Debt Securities [Member]
Number of investment positions - less than twelve months	22
Fair value - less than twelve months	$ 56,787
Gross unrealized losses - less than twelve months	$ 674
Number of investment positions - more than twelve months	1
Fair value - more than twelve months	$ 4,979
Gross unrealized losses - more than twelve months	$ 21
Agency Collateralized Mortgage Obligations [Member]
Number of investment positions - less than twelve months	13
Fair value - less than twelve months	$ 10,098
Gross unrealized losses - less than twelve months	$ 175
Number of investment positions - more than twelve months	6
Fair value - more than twelve months	$ 3,850
Gross unrealized losses - more than twelve months	$ 89
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Number of investment positions - less than twelve months	86
Fair value - less than twelve months	$ 113,326
Gross unrealized losses - less than twelve months	$ 1,987
Number of investment positions - more than twelve months	1
Fair value - more than twelve months	$ 504
Gross unrealized losses - more than twelve months	$ 12
Municipal Notes [Member]
Number of investment positions - less than twelve months	45
Fair value - less than twelve months	$ 24,057
Gross unrealized losses - less than twelve months	$ 924