Segment, Geographical and Other Revenue Information - Long-Lived Assets by Geographic Area (Details)	9 Months Ended	12 Months Ended
Sep. 30, 2018	Dec. 31, 2017
Net Assets, Geographic Area [Member] \| United States [Member]
Schedule of long-lived assets by geographical area
Long-lived assets	100.00%	100.00%

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.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
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