Customer, Supplier and Product Concentration - Percentage of the Company's Gross and Net Sales and Accounts Receivable (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Concentration Risk [Line Items]
Gross Accounts Receivable	$ 258,173				$ 308,305				$ 258,173	$ 308,305	$ 378,759
Gross sales									1,674,196	1,887,862	2,351,071
Revenues	162,257	$ 176,244	$ 178,057	$ 165,871	153,386	$ 165,625	$ 190,944	$ 184,063	682,429	694,018	841,045
Amerisource
Concentration Risk [Line Items]
Gross Accounts Receivable	56,945				55,160				56,945	55,160	99,771
Gross sales									348,030	386,543	554,690
Revenues									138,667	144,776	160,671
Cardinal
Concentration Risk [Line Items]
Gross Accounts Receivable	40,158				59,443				40,158	59,443	79,731
Gross sales									354,253	390,438	411,458
Revenues									115,489	109,747	150,257
McKesson
Concentration Risk [Line Items]
Gross Accounts Receivable	118,258				149,000				118,258	149,000	146,321
Gross sales									680,478	789,620	918,157
Revenues									157,572	173,363	222,715
Combined Total
Concentration Risk [Line Items]
Gross Accounts Receivable	215,361				263,603				215,361	263,603	325,823
Gross sales									1,382,761	1,566,601	1,884,305
Revenues									411,728	427,886	533,643
Other
Concentration Risk [Line Items]
Gross Accounts Receivable	$ 42,812				$ 44,702				42,812	44,702	52,936
Gross sales									291,435	321,261	466,766
Revenues									$ 270,701	$ 266,132	$ 307,402
Customer Concentration Risk | Gross Accounts Receivable
Concentration Risk [Line Items]
Customer concentration									100.00%	100.00%	100.00%
Customer Concentration Risk | Gross Sales
Concentration Risk [Line Items]
Customer concentration									100.00%	100.00%	100.00%
Customer Concentration Risk | Net Revenue
Concentration Risk [Line Items]
Customer concentration									100.00%	100.00%	100.00%
Customer Concentration Risk | Amerisource | Gross Accounts Receivable
Concentration Risk [Line Items]
Customer concentration									22.00%	17.90%	26.30%
Customer Concentration Risk | Amerisource | Gross Sales
Concentration Risk [Line Items]
Customer concentration									20.80%	20.50%	23.60%
Customer Concentration Risk | Amerisource | Net Revenue
Concentration Risk [Line Items]
Customer concentration									20.30%	20.90%	19.10%
Customer Concentration Risk | Cardinal | Gross Accounts Receivable
Concentration Risk [Line Items]
Customer concentration									15.60%	19.30%	21.10%
Customer Concentration Risk | Cardinal | Gross Sales
Concentration Risk [Line Items]
Customer concentration									21.20%	20.70%	17.50%
Customer Concentration Risk | Cardinal | Net Revenue
Concentration Risk [Line Items]
Customer concentration									16.90%	15.80%	17.90%
Customer Concentration Risk | McKesson | Gross Accounts Receivable
Concentration Risk [Line Items]
Customer concentration									45.80%	48.30%	38.60%
Customer Concentration Risk | McKesson | Gross Sales
Concentration Risk [Line Items]
Customer concentration									40.60%	41.80%	39.10%
Customer Concentration Risk | McKesson | Net Revenue
Concentration Risk [Line Items]
Customer concentration									23.10%	25.00%	26.50%
Customer Concentration Risk | Combined Total | Gross Accounts Receivable
Concentration Risk [Line Items]
Customer concentration									83.40%	85.50%	86.00%
Customer Concentration Risk | Combined Total | Gross Sales
Concentration Risk [Line Items]
Customer concentration									82.60%	83.00%	80.20%
Customer Concentration Risk | Combined Total | Net Revenue
Concentration Risk [Line Items]
Customer concentration									60.30%	61.70%	63.50%
Customer Concentration Risk | Other | Gross Accounts Receivable
Concentration Risk [Line Items]
Customer concentration									16.60%	14.50%	14.00%
Customer Concentration Risk | Other | Gross Sales
Concentration Risk [Line Items]
Customer concentration									17.40%	17.00%	19.80%
Customer Concentration Risk | Other | Net Revenue
Concentration Risk [Line Items]
Customer concentration									39.70%	38.30%	36.50%