Note 1 - Significant Accounting Policies and Concentrations of Risk (Details) - Fair Value of the Company’s Investments by Type (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 59,297	$ 19,421
Accrued Interest	179	48
Gross Unrealized Gains	5	5
Gross Unrealized Losses	(133)	(1)
Estimated Fair Value	59,348	19,473
US Government Agencies Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	20,307	4,899
Accrued Interest	22	1
Gross Unrealized Gains		1
Gross Unrealized Losses	(23)	0
Estimated Fair Value	20,306	4,901
Corporate Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	27,152	8,528
Accrued Interest	151	47
Gross Unrealized Gains	5	2
Gross Unrealized Losses	(47)	(1)
Estimated Fair Value	27,261	8,576
Commercial Paper [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	11,838	5,994
Accrued Interest	6	0
Gross Unrealized Gains		2
Gross Unrealized Losses	(63)	0
Estimated Fair Value	$ 11,781	$ 5,996