Summary of Business and Significant Accounting Policies - Financial Impact of ASU Adoption - Balance Sheet (Details) - USD ($) $ in Thousands	Jul. 01, 2019	Dec. 31, 2018	Jul. 02, 2018	Jun. 30, 2018
Financial impact of ASU adoption
Accounts receivable, net		$ 16,178	$ 22,213	$ 7,389
Costs capitalized to obtain revenue contracts, net		682	591	986
Costs capitalized to obtain revenue contracts, net of current portion		1,904	1,824	891
Accrued liabilities		1,746	2,345	2,285
Deferred revenue		28,836	30,064	18,364
Deferred revenue, net of current portion		6,136	7,411	7,833
Accumulated deficit		(346,840)	$ (349,444)	$ (353,260)
Impact
Financial impact of ASU adoption
Accounts receivable, net	$ 14,824	(9,036)
Costs capitalized to obtain revenue contracts, net	(395)	315
Costs capitalized to obtain revenue contracts, net of current portion	933	(1,137)
Accrued liabilities	60
Deferred revenue	11,700	(61)
Deferred revenue, net of current portion	(422)	(4,628)
Accumulated deficit	$ 3,816	3,816
Excluding Topic 606 Impact
Financial impact of ASU adoption
Accounts receivable, net		7,142
Costs capitalized to obtain revenue contracts, net		997
Costs capitalized to obtain revenue contracts, net of current portion		767
Deferred revenue		28,775
Deferred revenue, net of current portion		1,508
Accumulated deficit		$ (343,024)

Amount due from customers or clients, within one year of the balance sheet date (or the normal operating cycle, whichever is longer), for goods or services (including trade receivables) that have been delivered or sold in the normal course of business, reduced to the estimated net realizable fair value by an allowance established by the entity of the amount it deems uncertain of collection.

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