Commitments and Contingencies - Textual (Details)			1 Months Ended			3 Months Ended		9 Months Ended		12 Months Ended	24 Months Ended
	Jun. 30, 2017 USD ($)	Aug. 11, 2016 claim	Apr. 30, 2017 USD ($)	Feb. 28, 2017 USD ($)	Dec. 31, 2016 USD ($)	Sep. 30, 2017 USD ($) ft² building	Sep. 30, 2016 USD ($)	Sep. 30, 2017 USD ($) ft² building	Sep. 30, 2016 USD ($)	Dec. 31, 2012 USD ($)	Dec. 31, 2012 USD ($)
Commitments and Contingencies [Line Items]
Incentive from lessor					$ 1,300,000	$ 1,000,000		$ 1,000,000
Asset retirement obligations					400,000	400,000		400,000
Accretion expense related to asset retirement obligation						0	$ 0	0	$ 0
Non-current restricted cash					$ 1,624,000	1,536,000		1,536,000
Rent expense						1,000,000	900,000	2,800,000	2,600,000
Operating lease, sublease rentals						300,000	$ 300,000	1,000,000	$ 900,000
Capital leases, term of contract			3 years	3 years	3 years
Capital lease obligations incurred			$ 300,000	$ 400,000
Operating lease, future minimum sublease rentals						$ 1,500,000		$ 1,500,000
Claims dismissed | claim		5
Fifth Amendment [Member]
Commitments and Contingencies [Line Items]
Payments for capital improvements										$ 3,600,000
Tenant reimbursements											$ 3,100,000
Headquarters, Redwood City [Member] | Sixth Amendment [Member]
Commitments and Contingencies [Line Items]
Lease area space occupancy (square feet) | ft²						107,200		107,200
Number of buildings leased | building						4		4
Term Loan [Member]
Commitments and Contingencies [Line Items]
Borrowing capacity	$ 10,000,000
Revolving Credit Facility [Member]
Commitments and Contingencies [Line Items]
Borrowing capacity	$ 5,000,000
Accounts receivable borrowing base percentage	80.00%
Stated interest rate	5.00%
LIBOR [Member] | Term Loan [Member]
Commitments and Contingencies [Line Items]
Basis spread on variable rate	3.60%
Prime Rate [Member] | Revolving Credit Facility [Member]
Commitments and Contingencies [Line Items]
Basis spread on variable rate	1.00%
Minimum [Member]
Commitments and Contingencies [Line Items]
Expiration date of lease								Jan. 31, 2020
Maximum [Member]
Commitments and Contingencies [Line Items]
Expiration date of lease								Jan. 31, 2022
Standby Letters of Credit [Member]
Commitments and Contingencies [Line Items]
Non-current restricted cash					$ 800,000	$ 700,000		$ 700,000
Indemnification Agreement [Member]
Commitments and Contingencies [Line Items]
Loss contingency accrual					$ 0	$ 0		$ 0