Note 9 - Investments in Marketable Securities - Amortized Cost and Estimated Fair Value of Debt Securities as Available for Sale (Details) - USD ($)	Jun. 30, 2019	Dec. 31, 2018
Within 1 year, cost	$ 9,573,000	$ 11,448,000
Within 1 year, fair value	9,588,000	11,401,000
1 to 5 years, cost	92,116,000	98,487,000
1 to 5 years, fair value	93,733,000	97,430,000
6 to 10 years, cost	51,162,000	64,932,000
6 to 10 years, fair value	52,250,000	62,527,000
Over 10 years, cost	0	1,200,000
Over 10 years, fair value	0	1,235,000
Cost	152,851,000	176,067,000
Fair Value	$ 155,571,000	$ 172,593,000

Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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