Fair Value Measurements (Details) - Recurring - Fair value - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Assets:
Restricted cash	$ 260	$ 340
Total assets	40,377	74,189
Cash
Assets:
Cash and cash equivalents	2,114	10,348
Money market funds
Assets:
Cash and cash equivalents	38,003	63,501
Level 1
Assets:
Restricted cash	260	340
Total assets	40,377	74,189
Level 1 | Cash
Assets:
Cash and cash equivalents	2,114	10,348
Level 1 | Money market funds
Assets:
Cash and cash equivalents	$ 38,003	$ 63,501