Note 4 - Stockholders' Equity (Tables)

9 Months Ended

Sep. 30, 2014

Disclosure Text Block Supplement [Abstract]

Schedule of Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Table Text Block]

	Three Months Ended September 30,				Nine Months Ended September 30,
	2014		2013		2014		2013
Cost of Design-to-silicon yield-solutions	$	947	$	812	$	2,467	$	1,995
Research and development		426		484		1,230		1,143
Selling, general and administrative		853		628		2,562		1,804
Stock-based compensation expenses	$	2,226	$	1,924	$	6,259	$	4,942

Schedule of Share-based Payment Award, Stock Options, Valuation Assumptions [Table Text Block]

	Three Months Ended September 30,						Nine Months Ended September 30,
	2014			2013			2014			2013
Expected life (in years)		4.58			4.78			4.58			4.78
Volatility		44.88	%		50.30	%		43.45	%		55.83	%
Risk-free interest rate		1.63	%		1.31	%		1.55	%		0.94	%
Expected dividend		—			—			—			—
Weighted average fair value per share of options granted during the period	$	7.54		$	9.13		$	7.44		$	7.55

	Nine Months Ended September 30,
	2014			2013
Expected life (in years)		1.25			1.25
Volatility		33.46	%		45.29	%
Risk-free interest rate		0.21	%		0.19	%
Expected dividend		—			—
Weighted average fair value of purchase rights granted under the Purchase Plan	$	6.44		$	5.56

Schedule of Share-based Compensation, Stock Options, Activity [Table Text Block]

	Number of Options (in thousands)			Weighted Average Exercise Price per Share		Weighted Average Remaining Contractual Term (years)		Aggregate Intrinsic Value (in thousands)
Outstanding, January 1, 2014		2,880		$	7.35
Granted (weighted average fair value of $7.44 per share)		19		$	19.55
Exercised		(484	)	$	6.33
Canceled		(33	)	$	9.82
Expired		(6	)	$	5.91
Outstanding, September 30, 2014		2,376		$	7.63		5.96	$	12,428
Vested and expected to vest, September 30, 2014		2,344		$	7.59		5.93	$	12,316
Exercisable, September 30, 2014		1,762		$	7.14		5.41	$	9,895

Schedule of Share-based Compensation, Restricted Stock Units Award Activity [Table Text Block]

	Shares (in thousands)			Weighted Average Grant Date Fair Value Per Share
Nonvested, January 1, 2014		759		$	14.44
Granted		560		$	19.52
Vested		(167	)	$	13.77
Forfeited		(25	)	$	17.99
Nonvested, September 30, 2014		1,127		$	17.04