Commitments and Contingencies - Warranty (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Changes in the liability for product warranty claim costs
Balance at beginning of period	$ 35	$ 353	$ 41
Accruals for warranties issued during the period	102	23	1,178
Settlements (in cash or in kind) during the period	(3)	(341)	(866)
Balance at end of period	$ 134	$ 35	$ 353