Business and Summary of Significant Accounting Policies - Concentrations (Details)	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Revenue \| Sales method risk
Concentration Risk [Line Items]
Concentration risk, percentage	88.00%	83.00%	80.00%
One distributor \| Revenue \| Customer concentration risk
Concentration Risk [Line Items]
Concentration risk, percentage	46.00%	45.00%	42.00%
One distributor \| Accounts receivable \| Customer concentration risk
Concentration Risk [Line Items]
Concentration risk, percentage	46.00%	51.00%

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
-Publisher FASB
-Name Accounting Standards Codification
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Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
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Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
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