Available-for-Sale Securities (Details) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2016 USD ($) item	Sep. 30, 2016 USD ($) item
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis	$ 20,806	$ 20,806
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	(3)	(3)
Fair Value	$ 20,803	$ 20,803
Number of available-for-sale securities in an unrealized loss position | item	17	17
Number of available-for-sale securities in an unrealized loss position more than 12 months | item	0	0
Unrealized loss position, available-for-sale securities	$ 15,700	$ 15,700
Proceeds from sales of available for sale securities	0	7,800
Corporate Debt Securities
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis	18,746	18,746
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	(3)	(3)
Fair Value	18,743	18,743
U.S. Government-sponsored Securities
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis	2,060	2,060
Fair Value	$ 2,060	$ 2,060