Marketable Securities - AFS Debt Securities (Details) $ in Thousands	Sep. 30, 2016 USD ($)
Marketable securities available for sale, consisting of debt securities:
Amortized Cost	$ 9,176
Estimated Market Value	9,176
U.S. government agencies
Marketable securities available for sale, consisting of debt securities:
Amortized Cost	1,202
Estimated Market Value	1,202
Commercial paper
Marketable securities available for sale, consisting of debt securities:
Amortized Cost	7,974
Estimated Market Value	$ 7,974