Investments (Investments Held to Maturity) (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Gain (Loss) on Investments [Line Items]
Amortized Cost	$ 12,732	$ 14,083
Gross Unrealized Gain	0	0
Gross Unrealized (Loss)	(25)	(12)
Fair Value	12,707	14,071
Current assets
Gain (Loss) on Investments [Line Items]
Amortized Cost	12,732	14,083
Gross Unrealized Gain	0	0
Gross Unrealized (Loss)	(25)	(12)
Fair Value	12,707	14,071
Non current assets
Gain (Loss) on Investments [Line Items]
Amortized Cost	0	0
Gross Unrealized Gain	0	0
Gross Unrealized (Loss)	0	0
Fair Value	$ 0	$ 0