Segment Information - General (Details) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019 USD ($)	Sep. 30, 2018 USD ($)	Sep. 30, 2019 USD ($) segment	Sep. 30, 2018 USD ($)
Net product sales, cost of product sales and gross profit by product
Net product sales	$ 401.5	$ 412.7	$ 1,137.7	$ 1,246.4
Cost of product sales	33.0	51.9	88.8	166.8
Gross profit	368.5	360.8	$ 1,048.9	1,079.6
Segment disclosures
Number of operating segments | segment			1
Remodulin
Net product sales, cost of product sales and gross profit by product
Net product sales	168.3	153.6	$ 479.6	439.9
Cost of product sales	5.5	4.4	16.1	10.8
Gross profit	162.8	149.2	463.5	429.1
Tyvaso
Net product sales, cost of product sales and gross profit by product
Net product sales	110.8	107.8	324.2	308.3
Cost of product sales	6.9	6.9	14.8	14.3
Gross profit	103.9	100.9	309.4	294.0
Orenitram
Net product sales, cost of product sales and gross profit by product
Net product sales	62.0	53.8	174.4	155.5
Cost of product sales	3.5	3.9	12.3	9.9
Gross profit	58.5	49.9	162.1	145.6
Unituxin
Net product sales, cost of product sales and gross profit by product
Net product sales	30.1	22.9	80.1	60.7
Cost of product sales	4.1	4.2	11.4	9.9
Gross profit	26.0	18.7	68.7	50.8
Adcirca
Net product sales, cost of product sales and gross profit by product
Net product sales	30.3	74.6	79.4	282.0
Cost of product sales	13.0	32.5	34.2	121.9
Gross profit	$ 17.3	$ 42.1	$ 45.2	$ 160.1