Commitments and Contingencies - Lease Agreements (Details) $ in Thousands		1 Months Ended	12 Months Ended
	Jul. 31, 2015 ft²	Mar. 31, 2007	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Lease Arrangements
Loss Contingency Accrual			$ 0
Operating lease obligations
Total			3,327
2018			776
2019			500
2020			507
2021			515
2022			522
Therafter			507
Other contractual commitments
Total			10,550
2018			10,550
Future minimum contractual obligations and commitments
Total			13,877
2018			11,326
2019			500
2020			507
2021			515
2022			522
Therafter			507
Lease Agreement, Business and Research Premises
Lease Arrangements
Term of the lease agreement, under which it can only be terminated under certain conditions		10 years
Lease Agreement, Office Premises
Lease Arrangements
Leased office space (in square feet) | ft²	15,000
Lease Agreement, Equipment
Lease Arrangements
Lease expense			$ 1,264	$ 1,263	$ 861