Segment Information - General (Details) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017 USD ($)	Jun. 30, 2016 USD ($)	Jun. 30, 2017 USD ($) segment	Jun. 30, 2016 USD ($)
Net product sales, cost of product sales and gross profit by product
Net product sales	$ 444.6	$ 412.6	$ 815.1	$ 781.6
Cost of product sales	18.9	20.0	33.2	20.7
Gross profit	425.7	392.6	$ 781.9	760.9
Segment disclosures
Number of operating segments | segment			1
Remodulin
Net product sales, cost of product sales and gross profit by product
Net product sales	157.7	158.9	$ 303.5	298.7
Cost of product sales	3.9	3.0	5.9	0.6
Gross profit	153.8	155.9	297.6	298.1
Tyvaso
Net product sales, cost of product sales and gross profit by product
Net product sales	104.2	107.0	191.6	209.2
Cost of product sales	2.9	6.3	5.7	7.1
Gross profit	101.3	100.7	185.9	202.1
Adcirca
Net product sales, cost of product sales and gross profit by product
Net product sales	120.6	90.9	200.6	163.5
Cost of product sales	6.7	5.2	11.3	9.5
Gross profit	113.9	85.7	189.3	154.0
Orenitram
Net product sales, cost of product sales and gross profit by product
Net product sales	46.0	38.0	85.3	78.2
Cost of product sales	4.0	3.1	6.8	2.7
Gross profit	42.0	34.9	78.5	75.5
Unituxin
Net product sales, cost of product sales and gross profit by product
Net product sales	16.1	17.8	34.1	32.0
Cost of product sales	1.4	2.4	3.5	0.8
Gross profit	$ 14.7	$ 15.4	$ 30.6	$ 31.2