Segment Information - Additional Information (Details)	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2018 customer product	Sep. 30, 2017 customer	Sep. 30, 2018 customer segment product	Sep. 30, 2017 customer	Dec. 31, 2017
Segment Reporting Information [Line Items]
Number of operating segments | segment			1
Number of commercial products | product	2		2
Customer Concentration Risk | Sales Revenue, Net
Segment Reporting Information [Line Items]
Number of major customers	1	2	1	2
Customer concentration risk, percentage	67.00%	75.00%	69.00%	70.00%
Customer Concentration Risk | Accounts Receivable
Segment Reporting Information [Line Items]
Number of major customers	1		1
Customer concentration risk, percentage	50.00%	64.00%
Geographic Concentration Risk | Intangible Assets | Aegerion
Segment Reporting Information [Line Items]
Customer concentration risk, percentage			100.00%		100.00%
U.S. | Geographic Concentration Risk | Intangible Assets | Aegerion
Segment Reporting Information [Line Items]
Customer concentration risk, percentage			65.00%		65.00%
U.S. | Geographic Concentration Risk | Property and Equipment
Segment Reporting Information [Line Items]
Customer concentration risk, percentage			71.00%		75.00%
Europe | Geographic Concentration Risk | Intangible Assets | Aegerion
Segment Reporting Information [Line Items]
Customer concentration risk, percentage			35.00%		35.00%