Investments (Investments Held to Maturity) (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Gain (Loss) on Investments [Line Items]
Amortized Cost	$ 11,342	$ 14,083
Gross Unrealized Gain	0	0
Gross Unrealized (Loss)	(12)	(12)
Fair Value	11,330	14,071
Current assets
Gain (Loss) on Investments [Line Items]
Amortized Cost	11,342	14,083
Gross Unrealized Gain	0	0
Gross Unrealized (Loss)	(12)	(12)
Fair Value	11,330	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

Amount after other than temporary impairment (OTTI) accretion, of investments in debt securities classified as held-to-maturity.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 5
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=73527792&loc=d3e27232-111563

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 25
-Paragraph 1
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-URI http://asc.fasb.org/extlink&oid=65884222&loc=d3e22054-111558

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
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Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03.1)
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
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-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03.6)
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

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Amount of accumulated unrealized gain on investments in debt securities classified as held-to-maturity.

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