Summary of Significant Accounting Policies - Schedule of Major Categories of Sales-related Deductions (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Contract Charge-backs and Sales Volume Allowances
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Beginning balance	$ 453,703	$ 366,848	$ 330,811
Liabilities assumed from acquisitions	222,970
Provision related to sales recorded in the period	3,463,983	2,489,681	2,182,606
Credits/payments issued during the period	(3,311,060)	(2,402,826)	(2,146,569)
Ending balance	829,596	453,703	366,848
Cash Discount Allowances
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Beginning balance	20,408	18,438	14,894
Liabilities assumed from acquisitions	11,781
Provision related to sales recorded in the period	117,010	79,837	70,662
Credits/payments issued during the period	(113,042)	(77,867)	(67,118)
Ending balance	36,157	20,408	18,438
Accrued Returns Allowance
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Beginning balance	45,175	46,195	32,124
Liabilities assumed from acquisitions	102,502
Provision related to sales recorded in the period	85,996	24,571	31,741
Credits/payments issued during the period	(79,170)	(25,591)	(17,670)
Ending balance	154,503	45,175	46,195
Accrued Medicaid and Commercial Rebates
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Beginning balance	12,911	8,057	14,385
Liabilities assumed from acquisitions	51,618
Provision related to sales recorded in the period	104,664	25,982	17,181
Credits/payments issued during the period	(94,991)	(21,128)	(23,509)
Ending balance	$ 74,202	$ 12,911	$ 8,057