Summary of Significant Accounting Policies - Risk Concentration & Allowance for Doubtful Accounts (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2015 USD ($) item	Dec. 31, 2014 USD ($)
Risk Concentration
Number of major U.S. financial institutions with whom cash, cash equivalents and investments are maintained	2
Number of suppliers from whom certain components may be available	1
Accounts Receivable and Allowance for Doubtful Accounts
Allowance for Doubtful Accounts Receivable | $	$ 0	$ 0