Cash equivalents and marketable securities are comprised of debt securities, primarily U.S. government-backed and corporate obligations, which management believes to be high quality (investment grade) credit instruments.

The amortized cost, gross unrealized gains and losses and fair value of the Company's marketable debt and equity securities and investments at March 30, 2012 and December 31, 2011 were comprised of the following (in thousands):

	March 30, 2012

	Amortized cost		Unrealized gains		Unrealized losses			Fair value
Cash equivalents	$	65,850	$	—	$	—		$	65,850

Marketable securities
U.S. government agency notes	$	98,140	$	54	$	(9	)	$	98,185
Foreign government notes		1,765		1		—			1,766
Corporate debt securities		84,606		50		(28	)		84,628
Commercial paper		8,974		2		(2	)		8,974
Certificates of deposit		14,248		7		(1	)		14,254

	$	207,733	$	114	$	(40	)	$	207,807

Investments
U.S. government agency notes	$	31,636	$	7	$	(8	)	$	31,635
Corporate debt securities		24,444		26		(22	)		24,448
Certificates of deposit		2,500		2		(1	)		2,501

	$	58,580	$	35	$	(31	)	$	58,584

	December 31, 2011

	Amortized cost		Unrealized gains		Unrealized losses			Fair value
Cash equivalents	$	63,105	$	—	$	—		$	63,105

Marketable securities
U.S. government agency notes	$	106,631	$	100	$	(4	)	$	106,727
Foreign government notes		1,770		1		—			1,771
Corporate debt securities		73,218		52		(20	)		73,250
Commercial paper		22,787		1		(1	)		22,787
Certificates of deposit		19,548		8		(1	)		19,555

	$	223,954	$	162	$	(26	)	$	224,090

Investments
U.S. government agency notes	$	44,144	$	4	$	(18	)	$	44,130
Corporate debt securities		11,296		9		(8	)		11,297

	$	55,440	$	13	$	(26	)	$	55,427

The contractual maturity dates for the Company's available-for-sale securities that are classified as Marketable securities in the condensed consolidated balance sheets are one year or less from the respective balance sheet dates. The contractual maturity dates for the Company's available-for-sale securities that are classified as Investments in the condensed consolidated balance sheets are more than one year from the respective balance sheet dates.

The Company's financial assets or liabilities are measured using inputs from the three-tier fair value hierarchy, which is based on the level of independent, objective evidence surrounding the inputs used to measure fair value. A financial instrument's categorization within the fair value hierarchy is based upon the lowest level of input that is significant to the fair value measurement. The fair value hierarchy is as follows:

The following table shows the fair value of the Company's financial assets at March 30, 2012 and December 31, 2011. These financial assets are comprised of the Company's available-for-sale debt and equity securities and reported under the captions Cash and cash equivalents, Marketable securities and Investments in the condensed consolidated balance sheets (in thousands):

			Fair value measurements at March 30, 2012 using:

	Total carrying value at March 30, 2012		Quoted prices in active markets (Level 1)		Significant other observable inputs (Level 2)		Significant unobservable inputs (Level 3)
Cash equivalents	$	65,850	$	63,850	$	2,000	$	—

Marketable securities
U.S. government agency notes	$	98,185	$	—	$	98,185	$	—
Foreign government notes		1,766		—		1,766		—
Corporate debt securities		84,628		—		84,628		—
Commercial paper		8,974		—		8,974		—
Certificates of deposit		14,254		—		14,254		—

	$	207,807	$	—	$	207,807	$	—

Investments
U.S. government agency notes	$	31,635	$	—	$	31,635	$	—
Corporate debt securities		24,448		—		24,448		—
Certificates of deposit		2,501		—		2,501		—

	$	58,584	$	—	$	58,584	$	—

			Fair value measurements at December 31, 2011 using:

	Total carrying value at December 31, 2011		Quoted prices in active markets (Level 1)		Significant other observable inputs (Level 2)		Significant unobservable inputs (Level 3)
Cash equivalents	$	63,105	$	63,105	$	—	$	—

Marketable securities
U.S. government agency notes	$	106,727	$	—	$	106,727	$	—
Foreign government notes		1,771		—		1,771		—
Corporate debt securities		73,250		—		73,250		—
Commercial paper		22,787		—		22,787		—
Certificates of deposit		19,555		—		19,555		—

	$	224,090	$	—	$	224,090	$	—

Investments
U.S. government agency notes	$	44,130	$	—	$	44,130	$	—
Corporate debt securities		11,297		—		11,297		—

	$	55,427	$	—	$	55,427	$	—

The Company's marketable securities and investments have been valued on the basis of valuations provided by third-party pricing services, as derived from such services' pricing models. Inputs to the models may include, but are not limited to, reported trades, executable bid and asked prices, broker/dealer quotations, prices or yields of securities with similar characteristics, benchmark curves or information pertaining to the issuer, as well as industry and economic events. The pricing services may use a matrix approach, which considers information regarding securities with similar characteristics to determine the valuation for a security. The Company is ultimately responsible for the condensed consolidated financial statements and underlying estimates. Accordingly, the Company assesses the reasonableness of the valuations provided by the third-party pricing services by reviewing actual trade data, broker/dealer quotes and other similar data, which are obtained from quoted market prices or other sources.

- Definition

The entire disclosure for the fair value of financial instruments (as defined), including financial assets and financial liabilities (collectively, as defined), and the measurements of those instruments as well as disclosures related to the fair value of non-financial assets and liabilities. Such disclosures about the financial instruments, assets, and liabilities would include: (1) the fair value of the required items together with their carrying amounts (as appropriate); (2) for items for which it is not practicable to estimate fair value, disclosure would include: (a) information pertinent to estimating fair value (including, carrying amount, effective interest rate, and maturity, and (b) the reasons why it is not practicable to estimate fair value; (3) significant concentrations of credit risk including: (a) information about the activity, region, or economic characteristics identifying a concentration, (b) the maximum amount of loss the entity is exposed to based on the gross fair value of the related item, (c) policy for requiring collateral or other security and information as to accessing such collateral or security, and (d) the nature and brief description of such collateral or security; (4) quantitative information about market risks and how such risks are managed; (5) for items measured on both a recurring and nonrecurring basis information regarding the inputs used to develop the fair value measurement; and (6) for items presented in the financial statement for which fair value measurement is elected: (a) information necessary to understand the reasons for the election, (b) discussion of the effect of fair value changes on earnings, (c) a description of [similar groups] items for which the election is made and the relation thereof to the balance sheet, the aggregate carrying value of items included in the balance sheet that are not eligible for the election; (7) all other required (as defined) and desired information.

+ References

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+ Details