Investments (Investments Held to Maturity) (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Gain (Loss) on Securities [Line Items]
Amortized Cost	$ 1,252	$ 6,077
Gross Unrealized Gain	0	0
Gross Unrealized (Loss)	(1)	(6)
Fair Value	1,251	6,071
Current assets
Gain (Loss) on Securities [Line Items]
Amortized Cost	1,252	6,077
Gross Unrealized Gain	0	0
Gross Unrealized (Loss)	(1)	(6)
Fair Value	1,251	6,071
Non current assets
Gain (Loss) on Securities [Line Items]
Amortized Cost	0	0
Gross Unrealized Gain	0	0
Gross Unrealized (Loss)	0	0
Fair Value	$ 0	$ 0

Amount of investment in debt security measured at amortized cost (held-to-maturity).

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
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-Section 45
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Amount of accumulated unrecognized gain on investment in debt security measured at amortized cost (held-to-maturity).

+ References

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
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Amount of accumulated unrealized loss on investment in debt security measured at amortized cost (held-to-maturity).

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-Publisher FASB
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Fair value of investment in debt security measured at amortized cost (held-to-maturity).

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