Marketable Securities - Carrying Amounts of Marketable Securities (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Schedule of Marketable Securities [Line Items]
Short-term marketable securities	$ 25,043	$ 25,504
Long-term marketable securities	80,652	76,563
Level 1 [Member] | Held-to-Maturity [Member] | Reported Value Measurement [Member]
Schedule of Marketable Securities [Line Items]
Total marketable securities	105,695	102,067
Held-to-Maturity [Member]
Schedule of Marketable Securities [Line Items]
Short-term marketable securities	25,043	25,504
Long-term marketable securities	80,652	76,563
U.S. Government and agency obligations [Member] | Held-to-Maturity [Member]
Schedule of Marketable Securities [Line Items]
Short-term marketable securities	15,051	10,511
Long-term marketable securities	80,652	76,563
Commercial paper [Member] | Held-to-Maturity [Member]
Schedule of Marketable Securities [Line Items]
Short-term marketable securities	$ 9,992	$ 14,993