Financial Instruments (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014		Dec. 31, 2013
Fair value of asset measured on a recurring basis
Fixed income available-for-sale securities	$ 37,991		$ 42,987
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Fair value of asset measured on a recurring basis
Money market funds	10,252	[1]	5,254	[1]
Fixed income available-for-sale securities	0	[2]	0	[2]
Total	10,252		5,254
Significant Other Observable Inputs (Level 2) [Member]
Fair value of asset measured on a recurring basis
Money market funds	0	[1]	0	[1]
Fixed income available-for-sale securities	37,991	[2]	42,987	[2]
Total	37,991		42,987
Significant Unobservable Inputs (Level 3) [Member]
Fair value of asset measured on a recurring basis
Money market funds	0	[1]	0	[1]
Fixed income available-for-sale securities	0	[2]	0	[2]
Total	0		0
Fair Value, Measurements, Recurring [Member]
Fair value of asset measured on a recurring basis
Money market funds	10,252	[1]	5,254	[1]
Fixed income available-for-sale securities	37,991	[2]	42,987	[2]
Total	$ 48,243		$ 48,241

[1] Included in cash and cash equivalents in the Company’s condensed consolidated balance sheets

[2] Represents our portfolio of available for sale securities that is included in short-term investments in the Company’s condensed consolidated balance sheets