Note 2. Cash, Cash Equivalents and Available-for-Sale Securities

The fair value and the amortized cost of cash, cash equivalents, and available-for-sale securities by major security type at December 31, 2013 and 2012, are presented in the tables that follow.

As of December 31, 2013 (in thousands):

Cash and cash equivalents and available-for-sale securities	Amortized Cost			Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value

Cash and money market funds	$	103,262		$	—	$	—		$	103,262
U.S. Treasury securities		239,959			69		(4	)		240,024

Total		343,221			69		(4	)		343,286
Less amounts classified as cash equivalents		(103,262	)		—		—			(103,262	)

Total available-for-sale securities	$	239,959		$	69	$	(4	)	$	240,024

As of December 31, 2012 (in thousands):

Cash and cash equivalents and available-for-sale securities	Amortized Cost			Gross Unrealized Gains		Gross Unrealized Losses		Estimated Fair Value

Cash and money market funds	$	58,605		$	—	$	—	$	58,605
U.S. Treasury securities		155,948			33		—		155,981

Total		214,553			33		—		214,586
Less amounts classified as cash equivalents		(58,605	)		—		—		(58,605	)

Total available-for-sale securities	$	155,948		$	33	$	—	$	155,981

As of December 31, 2013, the Company's available-for-sale securities have original contractual maturities up to 23 months. However, the Company may or may not hold securities with stated maturities greater than 12 months until maturity. In response to changes in the availability of and the yield on alternative investments as well as liquidity requirements, the Company may sell these securities prior to their stated maturities. As these securities are viewed by the Company as available to support current operations, securities with maturities beyond 12 months are classified as current assets. Due to their short-term maturities, the Company believes that the fair value of its bank deposits, accounts payable and accrued expenses approximate their carrying value.

Fair Value Measurements

The authoritative literature for fair value measurements established a three-tier fair value hierarchy, which prioritizes the inputs in measuring fair value. These tiers are as follows: Level 1, defined as observable inputs such as quoted market prices in active markets; Level 2, defined as inputs other than the quoted prices in active markets that are either directly or indirectly observable; and Level 3, defined as significant unobservable inputs (entity developed assumptions) in which little or no market data exists.

As of December 31, 2013, and December 31, 2012, all of the Company's cash and cash equivalents and available-for-sale securities were measured at fair value on a recurring basis, and classified as Level 1 in the fair value hierarchy. There were no assets or liabilities measured on a recurring basis where Level 2 or Level 3 valuation techniques were used.