Short-term and Long-term Investments (Tables)

3 Months Ended

Mar. 31, 2015

Investments, Debt and Equity Securities [Abstract]

Summary of Amortized Cost, Gross Unrealized Gains and Losses and Fair Value of Investments

The following table summarizes the amortized cost, gross unrealized gains and losses and fair value of available-for-sale investments as of March 31, 2015:



	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Aggregate Fair Value
U.S. government debt securities	$	91,169	$	69	$	—	$	91,238
Certificates of deposit	272		—		—		272
Total	$	91,441	$	69	$	—	$	91,510

The following table summarizes the amortized cost, gross unrealized gains and losses and fair value of available-for-sale investments as of December 31, 2014:



	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Aggregate Fair Value
U.S. government debt securities	$	115,293	$	54	$	(12	)	$	115,335
Certificates of deposit	273		—		—			273
Total	$	115,566	$	54	$	(12	)	$	115,608

Summary of Estimated Fair Value of Available-for-Sale Investments Classified by Contractual Maturities

The estimated fair value of available-for-sale investments classified by their contractual maturities as of March 31, 2015 was as follows:



Due within one year	$	82,461
After one year through two years	9,049
Total	$	91,510

- Definition

Tabular disclosure of available-for-sale securities which includes, but is not limited to, changes in the cost basis and fair value, fair value and gross unrealized gain (loss), fair values by type of security, contractual maturity and classification, amortized cost basis, contracts to acquire securities to be accounted for as available-for-sale, debt maturities, transfers to trading, change in net unrealized holding gain (loss) net of tax, continuous unrealized loss position fair value, aggregate losses qualitative disclosures, other than temporary impairment (OTTI) losses or other disclosures related to available for sale securities.

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