Fair Value Measurement Cash and Cash Equivalents (Details) - Fair Value, Measurements, Recurring - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016	Mar. 31, 2016
Assets, Fair Value Disclosure
Total Assets, Fair Value	$ 28,091	$ 10,057	$ 46,094
Level 1
Assets, Fair Value Disclosure
Total Assets, Fair Value	28,091	10,057	46,094
Level 2
Assets, Fair Value Disclosure
Total Assets, Fair Value	0	0	0
Level 3
Assets, Fair Value Disclosure
Total Assets, Fair Value	0	0	0
Money Market Funds
Assets, Fair Value Disclosure
Cash equivalents	28,091	10,057	46,094
Money Market Funds | Level 1
Assets, Fair Value Disclosure
Cash equivalents	28,091	10,057	46,094
Money Market Funds | Level 2
Assets, Fair Value Disclosure
Cash equivalents	0	0	0
Money Market Funds | Level 3
Assets, Fair Value Disclosure
Cash equivalents	$ 0	$ 0	$ 0