Note 5 - Accumulated Other Comprehensive Income (Details) - Changes in Accumulated Other Comprehensive Income (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Unrealized gains (losses) on available-for-sale marketable securities (1) :
Ending balance	$ 10,455	[1]	$ 11,575	[1]	$ 4,838	[1]
Accumulated Net Unrealized Investment Gain (Loss) [Member] | Metropolitan District Bond Securities [Member]
Unrealized gains (losses) on available-for-sale marketable securities (1) :
Beginning balance	3,920	[1]		[1]		[1]
Ending balance	7,680	[1]	3,920	[1]		[1]
Other comprehensive income before reclassifications	3,760	[1]	3,920	[1]		[1]
Amounts reclassified from accumulated other comprehensive income	0	[1]	0	[1]	0	[1]
Accumulated Net Unrealized Investment Gain (Loss) [Member]
Unrealized gains (losses) on available-for-sale marketable securities (1) :
Beginning balance	7,655	[1]	4,838	[1]	(7,240)	[1]
Ending balance	2,775	[1]	7,655	[1]	4,838	[1]
Other comprehensive income before reclassifications	(3,025)	[1]	3,255	[1]	12,473	[1]
Amounts reclassified from accumulated other comprehensive income	$ (1,855)	[1],[2]	$ (438)	[1],[2]	$ (395)	[1],[2]

[1] All amounts net-of-tax.

[2] See separate table below for details about these reclassifications.