Significant Accounting Policies (Tables)

3 Months Ended

Mar. 31, 2014

Significant Accounting Policies [Abstract]

Changes in other accumulated other comprehensive income related to unrealized gains and losses on securities

The following table summarizes changes in accumulated other comprehensive income for the three months ended March 31, 2014 and 2013 (in thousands):

	Three Months Ended March 31,
	2014			2013
Beginning balance accumulated other comprehensive income	$	21,080		$	12,480
Other comprehensive income before reclassifications, net of tax (1)		8,261			6,467
Amounts reclassified from accumulated other comprehensive income (2)		(341	)		(1,163	)
Net current period other comprehensive income		7,920			5,304
Ending balance accumulated other comprehensive income	$	29,000		$	17,784

(1) Other comprehensive income includes income tax expense of $5.4 million and $3.6 million for the three months ended March 31, 2014 and 2013, respectively.

(2) Included in gain on investments, net on our condensed consolidated statement of operations.

Stock-based compensation expense

Schedule of weighted-average assumptions used for valuation of ESPP

ESPP:

	Three Months Ended March 31,
	2014			2013
Risk-free interest rate		0.1	%		0.1	%
Dividend yield		0.0	%		0.0	%
Volatility		59.0	%		61.4	%
Expected life	6 months			6 months

Schedule of stock-based compensation expense

The following table summarizes stock-based compensation expense for the three months ended March 31, 2014 and 2013 (in thousands), which was allocated as follows:

	Three Months Ended March 31,
	2014		2013
Research, development and patent expenses	$	5,873	$	2,546
General and administrative		1,196		323
Total	$	7,069	$	2,869

Employee Stock Options [Member]

Stock-based compensation expense

Schedule of weighted-average assumptions used for valuation of stock options

Employee Stock Options:

	Three Months Ended March 31,
	2014			2013
Risk-free interest rate		1.6	%		1.0	%
Dividend yield		0.0	%		0.0	%
Volatility		50.5	%		51.5	%
Expected life	4.6 years			5.1 years

Board of Director Stock Option [Member]

Stock-based compensation expense

Schedule of weighted-average assumptions used for valuation of stock options

Board of Director Stock Options:

	Three Months Ended March 31,
	2014
Risk-free interest rate		2.3	%
Dividend yield		0.0	%
Volatility		53.3	%
Expected life	7.1 years