Short-term and Long-term Investments (Tables)

3 Months Ended

Mar. 31, 2014

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, 2014:

	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Aggregate Fair Value
U.S. government debt securities	$	148,861	$	91	$	(1	)	$	148,951
Commercial paper		1,999		—		—			1,999
Certificates of deposit		2,017		—		—			2,017
Total	$	152,877	$	91	$	(1	)	$	152,967

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, 2014 was as follows:

Due within one year	$	112,755
After one year through two years		40,212
Total	$	152,967