Segment Information - General (Details) $ in Millions	3 Months Ended
	Mar. 31, 2019 USD ($) segment	Mar. 31, 2018 USD ($)
Net product sales, cost of product sales and gross profit by product
Net product sales	$ 362.6	$ 389.2
Cost of product sales	29.1	53.2
Gross profit	$ 333.5	336.0
Segment disclosures
Number of operating segments | segment	1
Remodulin
Net product sales, cost of product sales and gross profit by product
Net product sales	$ 155.5	126.8
Cost of product sales	6.1	3.0
Gross profit	149.4	123.8
Tyvaso
Net product sales, cost of product sales and gross profit by product
Net product sales	103.8	94.6
Cost of product sales	4.4	3.0
Gross profit	99.4	91.6
Orenitram
Net product sales, cost of product sales and gross profit by product
Net product sales	24.9	18.0
Cost of product sales	5.1	2.3
Gross profit	19.8	15.7
Unituxin
Net product sales, cost of product sales and gross profit by product
Net product sales	20.0	97.6
Cost of product sales	8.7	41.9
Gross profit	11.3	55.7
Adcirca
Net product sales, cost of product sales and gross profit by product
Net product sales	58.4	52.2
Cost of product sales	4.8	3.0
Gross profit	$ 53.6	$ 49.2