Marketable Securities - Carrying Amounts of Marketable Securities (Details) - USD ($) $ in Thousands |
Sep. 30, 2015 |
Dec. 31, 2014 |
Sep. 30, 2014 |
---|---|---|---|
Schedule of Marketable Securities [Line Items] | |||
Short-term marketable securities | $ 17,607 | $ 25,504 | $ 27,950 |
Long-term marketable securities | 70,646 | 76,563 | 74,140 |
Held-to-Maturity [Member] | |||
Schedule of Marketable Securities [Line Items] | |||
Short-term marketable securities | 17,607 | 25,504 | 27,950 |
Long-term marketable securities | 70,646 | 76,563 | 74,140 |
Total marketable securities | 88,253 | 102,067 | 102,090 |
U.S. Government and agency obligations [Member] | Held-to-Maturity [Member] | |||
Schedule of Marketable Securities [Line Items] | |||
Short-term marketable securities | 7,625 | 10,511 | 12,967 |
Long-term marketable securities | 70,646 | 76,563 | 74,140 |
Commercial paper [Member] | Held-to-Maturity [Member] | |||
Schedule of Marketable Securities [Line Items] | |||
Short-term marketable securities | $ 9,982 | $ 14,993 | $ 14,983 |