Segment Information - General (Details) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017 USD ($)	Sep. 30, 2016 USD ($)	Sep. 30, 2017 USD ($) segment	Sep. 30, 2016 USD ($)
Net product sales, cost of product sales and gross profit by product
Net product sales	$ 445.5	$ 408.2	$ 1,260.6	$ 1,189.8
Cost of product sales	19.5	23.6	52.7	44.3
Gross profit	426.0	384.6	$ 1,207.9	1,145.5
Segment disclosures
Number of operating segments | segment			1
Remodulin
Net product sales, cost of product sales and gross profit by product
Net product sales	187.3	152.4	$ 490.8	451.1
Cost of product sales	4.0	3.7	9.9	4.3
Gross profit	183.3	148.7	480.9	446.8
Tyvaso
Net product sales, cost of product sales and gross profit by product
Net product sales	88.9	101.8	280.5	311.0
Cost of product sales	2.2	5.8	7.9	12.9
Gross profit	86.7	96.0	272.6	298.1
Adcirca
Net product sales, cost of product sales and gross profit by product
Net product sales	99.8	96.0	300.4	259.5
Cost of product sales	5.6	5.5	16.9	15.0
Gross profit	94.2	90.5	283.5	244.5
Orenitram
Net product sales, cost of product sales and gross profit by product
Net product sales	52.5	40.7	137.8	118.9
Cost of product sales	3.9	5.2	10.7	7.9
Gross profit	48.6	35.5	127.1	111.0
Unituxin
Net product sales, cost of product sales and gross profit by product
Net product sales	17.0	17.3	51.1	49.3
Cost of product sales	3.8	3.4	7.3	4.2
Gross profit	$ 13.2	$ 13.9	$ 43.8	$ 45.1