Fair Value Measurements - Recurring (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Fair Value, Net Asset (Liability)
Fair Value, Assets, Level 1 to Level 2 Transfers, Amount	$ 0	$ 0
Fair Value, Assets, Level 2 to Level 1 Transfers, Amount	0	0
Fair Value, Liabilities, Level 1 to Level 2 Transfers, Amount	0	0
Fair Value, Liabilities, Level 2 to Level 1 Transfers, Amount	0	0
Fair value assets level 3 net transfers	0	0
Fair value liabilities level 3 net transfers	0	0
Recurring
Fair Value, Net Asset (Liability)
Cash and cash equivalents	50,015	55,066
Short-term investments	15,793	82,282
Contingent liability	3,678	3,408
Level 1 | Recurring
Fair Value, Net Asset (Liability)
Cash and cash equivalents	50,015	55,066
Level 2 | Recurring
Fair Value, Net Asset (Liability)
Short-term investments	15,793	82,282
Level 3 | Recurring
Fair Value, Net Asset (Liability)
Contingent liability	$ 3,678	$ 3,408