Revenue Recognition - Cumulative Effect of ASU 2014-09 (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Apr. 01, 2018	Mar. 31, 2018
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Inventory	$ 18,353		$ 19,780
Prepaid expenses and other current assets	4,709		2,947
Note receivable	2,720		2,559
Accounts payable and accrued expenses	(15,144)		(12,625)
Deferred revenue	(8,040)		(8,454)
Accumulated deficit	$ (993,037)		(988,333)
Accounting Standards Update 2014-09
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Inventory		$ 18,181
Prepaid expenses and other current assets		4,546
Note receivable		2,664
Accounts payable and accrued expenses		(15,354)
Deferred revenue		(10,826)
Accumulated deficit		$ (988,366)
Difference between Revenue Guidance in Effect before and after Topic 606 | Accounting Standards Update 2014-09
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Inventory			(1,599)
Prepaid expenses and other current assets			1,599
Note receivable			105
Accounts payable and accrued expenses			(2,729)
Deferred revenue			2,657
Accumulated deficit			(33)
Calculated under Revenue Guidance in Effect before Topic 606 | Accounting Standards Update 2014-09
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Inventory			19,780
Prepaid expenses and other current assets			2,947
Note receivable			2,559
Accounts payable and accrued expenses			(12,625)
Deferred revenue			(13,483)
Accumulated deficit			$ (988,333)