Segment Information - General (Details) $ in Millions	3 Months Ended
	Mar. 31, 2017 USD ($) segment	Mar. 31, 2016 USD ($)
Net product sales, cost of product sales and gross profit by product
Net product sales	$ 370.5	$ 369.0
Cost of product sales	14.3	0.7
Gross profit	$ 356.2	368.3
Segment disclosures
Number of operating segments | segment	1
Remodulin
Net product sales, cost of product sales and gross profit by product
Net product sales	$ 145.8	139.8
Cost of product sales	2.0
Cost of product sales		(2.4)
Gross profit	143.8	142.2
Tyvaso
Net product sales, cost of product sales and gross profit by product
Net product sales	87.4	102.2
Cost of product sales	2.8	0.8
Gross profit	84.6	101.4
Adcirca
Net product sales, cost of product sales and gross profit by product
Net product sales	80.0	72.6
Cost of product sales	4.6	4.3
Gross profit	75.4	68.3
Orenitram
Net product sales, cost of product sales and gross profit by product
Net product sales	39.3	40.2
Cost of product sales	2.8
Cost of product sales		(0.4)
Gross profit	36.5	40.6
Unituxin
Net product sales, cost of product sales and gross profit by product
Net product sales	18.0	14.2
Cost of product sales	2.1
Cost of product sales		(1.6)
Gross profit	$ 15.9	$ 15.8