Financial Instruments (Details) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015	Sep. 30, 2015	Dec. 31, 2014
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Transfers Between Fair Value Measurement Levels	$ 0		$ 0
Cash and Cash Equivalents
Cash and Cash Equivalents, at Carrying Value	26,464	$ 62,780	$ 72,709	$ 14,668
Available-for-Sale Securities:
Available-for-sale Securities	20,803
Corporate Debt Securities
Available-for-Sale Securities:
Available-for-sale Securities	18,743
U.S. Government-sponsored Securities
Available-for-Sale Securities:
Available-for-sale Securities	2,060
Level 1
Assets:
Total assets	23,396	62,004
Level 1 | Money market funds
Cash and Cash Equivalents
Cash and Cash Equivalents, at Carrying Value	23,396	62,004
Level 2
Assets:
Total assets	21,623
Level 2 | Corporate Debt Securities
Available-for-Sale Securities:
Available-for-sale Securities	18,743
Level 2 | U.S. Government-sponsored Securities
Cash and Cash Equivalents
Cash and Cash Equivalents, at Carrying Value	820
Available-for-Sale Securities:
Available-for-sale Securities	2,060
Recurring
Assets:
Total assets	45,019	62,004
Recurring | Money market funds
Cash and Cash Equivalents
Cash and Cash Equivalents, at Carrying Value	23,396	$ 62,004
Recurring | Corporate Debt Securities
Available-for-Sale Securities:
Available-for-sale Securities	18,743
Recurring | U.S. Government-sponsored Securities
Cash and Cash Equivalents
Cash and Cash Equivalents, at Carrying Value	820
Available-for-Sale Securities:
Available-for-sale Securities	$ 2,060