Note 5 - Securities Available-for-Sale (Details) - Securities Available-for-Sale (USD $) In Thousands, unless otherwise specified	6 Months Ended	12 Months Ended
	Jun. 30, 2014	Dec. 31, 2013
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 14,376	$ 33,311
Unrealized Gain	3	4
Unrealized Loss		(5)
Estimated Fair Value	14,379	33,310
Commercial Paper, Not Included with Cash and Cash Equivalents [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	9,498	9,798
Estimated Fair Value	9,498	9,798
US Government-sponsored Enterprises Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	2,006	17,007
Unrealized Gain		2
Unrealized Loss		(4)
Estimated Fair Value	2,006	17,005
Corporate Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	2,872	6,506
Unrealized Gain	3	2
Unrealized Loss		(1)
Estimated Fair Value	$ 2,875	$ 6,507