Investments (Details) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 1,799	$ 1,799
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(23)	(23)
Fair Value	1,776	1,776
U.S. government security funds
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	1,799	1,799
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(23)	(23)
Fair Value	$ 1,776	$ 1,776