Basis of Presentation and Summary of Significant Accounting Policies - Textual (Details)	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2017 USD ($)	Sep. 30, 2016 USD ($)	Sep. 30, 2017 USD ($) operating_segment	Sep. 30, 2016 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Loss Contingencies [Line Items]
Cash and cash equivalents	$ 23,826,000	$ 14,918,000	$ 23,826,000	$ 14,918,000	$ 19,240,000	$ 23,273,000
Cash	17,500,000		17,500,000		8,000,000
Money market funds	6,300,000		6,300,000		11,200,000
restricted cash deposit balances	1,536,000		1,536,000		1,624,000
Impairment charge			$ 0		0
Number of operating segments | operating_segment			1
Number of reportable segments | operating_segment			1
Goodwill impairment			$ 0		0
Expense (benefit) from income taxes	150,000	$ 0	132,000	$ (15,000)
Financial Standby Letter of Credit [Member]
Loss Contingencies [Line Items]
restricted cash deposit balances	700,000		700,000		800,000
India [Member]
Loss Contingencies [Line Items]
Non-current restricted cash	$ 800,000		$ 800,000		$ 800,000