Revenues - Summary of the Percentage of Total Revenues from Customers (Details) - Total Revenues - Customer concentration risk	3 Months Ended	6 Months Ended
Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Express Scripts
Concentration Risk [Line Items]
Percentage of total revenues (as a percent)	77.00%	71.00%	75.00%	71.00%
McKesson
Concentration Risk [Line Items]
Percentage of total revenues (as a percent)	12.00%	20.00%	15.00%	20.00%

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.

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