Marketable Securities - Additional Information (Details) - USD ($)	9 Months Ended	12 Months Ended
	Sep. 30, 2016	Dec. 31, 2015
Investments Debt And Equity Securities [Abstract]
Unrealized loss position on aggregate fair value of investments	$ 17,138,000
Unrealized loss on marketable securities		$ 0
Gross realized gains or losses from sale or maturity of marketable securities	0	0
Gross interest income on securities	173,000	30,000
Amortization expense on securities	$ 20,000	$ 13,000