Significant Accounting Policies (Concentration of Credit Risk, Accounts Receivable, and Allowance for Doubtful Accounts) (Narrative) (Details)	12 Months Ended
Dec. 31, 2018 USD ($) customer	Dec. 31, 2017 USD ($) customer	Dec. 31, 2016 USD ($) customer
Concentration Risk [Line Items]
Bad debt expense \| $	$ 0	$ 200,000	$ 200,000
Customer Concentration Risk [Member]
Concentration Risk [Line Items]
Concentration risk, number of customer \| customer	1	1	1
Sales Revenue, Net [Member] \| Customer Concentration Risk [Member]
Concentration Risk [Line Items]
Concentration risk, percentage	18.00%	17.00%	20.00%
Sales Revenue, Net [Member] \| Geographic Concentration Risk [Member]
Concentration Risk [Line Items]
Concentration risk, percentage	8.00%	9.00%	9.00%
Accounts Receivable [Member] \| Customer Concentration Risk [Member]
Concentration Risk [Line Items]
Concentration risk, percentage	6.00%	3.00%	4.00%

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

No definition available.

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For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 275
-SubTopic 10
-Section 50
-Paragraph 18
-URI http://asc.fasb.org/extlink&oid=99393423&loc=d3e6351-108592

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-Publisher FASB
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-Topic 825
-SubTopic 10
-Section 50
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-Publisher FASB
-Name Accounting Standards Codification
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-Paragraph 21
-Subparagraph (a)
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-Publisher FASB
-Name Accounting Standards Codification
-Topic 275
-SubTopic 10
-Section 50
-Paragraph 20
-URI http://asc.fasb.org/extlink&oid=99393423&loc=d3e6404-108592

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Amount of expense related to write-down of receivables to the amount expected to be collected. Includes, but is not limited to, accounts receivable and notes receivable.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.5)
-URI http://asc.fasb.org/extlink&oid=115205541&loc=SL114868664-224227

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 45
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=82913815&loc=SL49130534-203044

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Concentration Risk, Number of Entities Included In Calculation

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