Summary of Significant Accounting Policies - Revenue Recognition - Condensed Balance Sheet (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Summary of Significant Accounting Policies
Accumulated deficit	$ (117,516)	$ (117,539)
Current assets:
Accounts receivable, net	8,904	3,429
Inventory	8,903	9,837
Total current assets	53,279	27,418
Total assets	57,147	31,437
Current liabilities:
Deferred income on shipments to distributors		1,720
Total current liabilities	13,688	12,375
Total liabilities	20,460	20,553
Stockholders' equity:
Accumulated deficit	(117,516)	(117,539)
Total liabilities and stockholders' equity	57,147	31,437
ASU 2014-09 | Balances without the adoption of Topic 606
Summary of Significant Accounting Policies
Accumulated deficit	(119,324)
Current assets:
Accounts receivable, net	9,267
Inventory	8,929
Total current assets	53,668
Total assets	57,536
Current liabilities:
Deferred income on shipments to distributors	2,197
Total current liabilities	15,885
Total liabilities	22,657
Stockholders' equity:
Accumulated deficit	(119,324)
Total liabilities and stockholders' equity	57,536
ASU 2014-09 | Adjustments
Summary of Significant Accounting Policies
Accumulated deficit	(1,808)	1,300
Current assets:
Accounts receivable, net	363
Inventory	26
Total current assets	389
Total assets	389
Current liabilities:
Deferred income on shipments to distributors	2,197
Total current liabilities	2,197
Total liabilities	2,197
Stockholders' equity:
Accumulated deficit	(1,808)	$ 1,300
Total liabilities and stockholders' equity	$ 389