Income taxes (Deferred Tax Assets) (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Current deferred tax assets
Net operating loss carryforwards	$ 2,179	$ 333
Inventory valuation	14	33
Reserves and allowances	2,394	1,791
Net current deferred tax assets	4,587	2,157
Net operating loss carryforwards	44,228	51,598
Research and development and other credit carryforwards	5,414	4,488
Fixed assets and intangibles	(1,705)	(2,819)
Net non-current deferred tax assets	47,937	53,267
Valuation allowance	(4,901)	(5,562)
Total	$ 47,623	$ 49,862