Fair Value Measurements (Detail Textuals) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014	Mar. 31, 2014	Dec. 31, 2013
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents, primarily include money market funds	$ 44,685	$ 43,985	$ 74,368	$ 72,660
Fair value on recurring basis | Corporate debt securities | Fair Value Measurement, Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investments	925	1,428
Fair value on recurring basis | Money market funds (included in cash and cash equivalents) | Fair Value Measurement, Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents, primarily include money market funds	$ 34,900	$ 34,300