Fair Value Measurements - Recurring (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	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	55,781		$ 55,066
Short-term investments	56,698		82,282
Contingent liability (included in other liabilities)	3,382		3,408
Level 1 | Recurring
Fair Value, Net Asset (Liability)
Cash and cash equivalents	55,781		55,066
Short-term investments	13,954
Level 2 | Recurring
Fair Value, Net Asset (Liability)
Short-term investments	42,744		82,282
Level 3 | Recurring
Fair Value, Net Asset (Liability)
Contingent liability (included in other liabilities)	$ 3,382		$ 3,408