Note 7 - Stockholders' Equity and Stock-based Compensation Expense - Activity Under the 2004 Equity Incentive Plan (Details)	3 Months Ended
	Mar. 31, 2017 $ / shares shares
Balance, shares available for grant (in shares)	721,657
Balance, stock options outstanding (in shares)	1,116,472
Balance, weighted-average exercise price (in dollars per share) | $ / shares	$ 9.56
Options granted, shares available for grant (in shares)	(52,000)
Options granted, stock options outstanding (in shares)	52,000
Options granted, weighted-average exercise price (in dollars per share) | $ / shares	$ 18.18
Stock awards granted(1) (2) (in shares)	(449,440)	[1],[2]
Options exercised, stock options outstanding (in shares)	(201,686)
Options exercised, weighted-average exercise price (in dollars per share) | $ / shares	$ 8.68
Options canceled, shares available for grant (in shares)	11,352
Options canceled, stock options outstanding (in shares)	(11,352)
Options canceled, weighted-average exercise price (in dollars per share) | $ / shares	$ 17.39
Stock awards canceled(1) (in shares)	94,113	[2]
Balance, shares available for grant (in shares)	325,682
Balance, stock options outstanding (in shares)	955,434
Balance, weighted-average exercise price (in dollars per share) | $ / shares	$ 10.12

[1] Included in 'Stock awards granted' of 449,440, was 221,540 fungible shares relating to 104,500 of PSUs granted. These PSUs mayresult in a lower number of shares of common stock that may be released on January 1, 2018, based on the achievement of two performance goals at targets that were pre-determined by the Board and disclosed in a Form 8-K on January 11, 2017.

[2] The Company has a "fungible share" provision in its 2004 Equity Incentive Plan whereby for each full-value award (RSU/PSU) issued or canceled under the Plan requires the subtraction or add back of 2.12 shares from or to the Shares Available for Grant, respectively.