Note 7 - Securities Available for Sale - Securities in a Continuous Unrealized Loss Position (Details)	Sep. 30, 2016 USD ($)	Dec. 31, 2015 USD ($)
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member] | Federal National Mortgage Association Certificates and Obligations (FNMA) [Member]
Number of investments, less than twelve months	1	1
Fair value, less than twelve months	$ 168,000	$ 346,000
Unrealized losses, less than twelve months	$ (4,000)	$ (1,000)
Number of investments, twelve months or more	0	0
Fair value, twelve months or more	$ 0	$ 0
Unrealized losses, twelve months or more	0	0
Fair Value	168,000	346,000
Unrealized Losses	(4,000)	(1,000)
Fair value, twelve months or more	$ 0	$ 0
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member] | Other Long-term Investments [Member]
Number of investments, less than twelve months	1	2
Fair value, less than twelve months	$ 8,000	$ 34,000
Unrealized losses, less than twelve months	$ (1,000)	$ (8,000)
Number of investments, twelve months or more	0	0
Fair value, twelve months or more	$ 0	$ 0
Unrealized losses, twelve months or more	0	0
Fair Value	8,000	34,000
Unrealized Losses	(1,000)	(8,000)
Fair value, twelve months or more	$ 0	$ 0
Other Marketable Securities [Member] | US Government Agencies Debt Securities [Member]
Number of investments, less than twelve months	2	9
Fair value, less than twelve months	$ 9,995,000	$ 44,878,000
Unrealized losses, less than twelve months	$ (5,000)	$ (129,000)
Number of investments, twelve months or more	0	0
Fair value, twelve months or more	$ 0	$ 0
Unrealized losses, twelve months or more	0	0
Fair Value	9,995,000	44,878,000
Unrealized Losses	(5,000)	(129,000)
Fair value, twelve months or more	$ 0	$ 0
Other Marketable Securities [Member] | US States and Political Subdivisions Debt Securities [Member]
Number of investments, less than twelve months	0	12
Fair value, less than twelve months	$ 0	$ 2,010,000
Unrealized losses, less than twelve months	$ 0	$ (7,000)
Number of investments, twelve months or more	3	0
Fair value, twelve months or more	$ 341,000	$ 0
Unrealized losses, twelve months or more	(2,000)	0
Fair Value	341,000	2,010,000
Unrealized Losses	(2,000)	(7,000)
Fair value, twelve months or more	$ 341,000	$ 0
Other Marketable Securities [Member] | Preferred Stock [Member]
Number of investments, less than twelve months	0	0
Fair value, less than twelve months	$ 0	$ 0
Unrealized losses, less than twelve months	$ 0	$ 0
Number of investments, twelve months or more	1	1
Fair value, twelve months or more	$ 350,000	$ 350,000
Unrealized losses, twelve months or more	(350,000)	(350,000)
Fair Value	350,000	350,000
Unrealized Losses	(350,000)	(350,000)
Fair value, twelve months or more	$ 350,000	$ 350,000
Other Marketable Securities [Member] | Corporate Debt Securities [Member]
Number of investments, less than twelve months		1
Fair value, less than twelve months		$ 334,000
Unrealized losses, less than twelve months		$ (6,000)
Number of investments, twelve months or more		0
Fair value, twelve months or more		$ 0
Unrealized losses, twelve months or more		0
Fair Value		334,000
Unrealized Losses		(6,000)
Fair value, twelve months or more		$ 0
Number of investments, less than twelve months	4	25
Fair value, less than twelve months	$ 10,171,000	$ 47,602,000
Unrealized losses, less than twelve months	$ (10,000)	$ (151,000)
Number of investments, twelve months or more	4	1
Fair value, twelve months or more	$ 691,000	$ 350,000
Unrealized losses, twelve months or more	(352,000)	(350,000)
Fair Value	10,862,000	47,952,000
Unrealized Losses	(362,000)	(501,000)
Fair value, twelve months or more	$ 691,000	$ 350,000