Capitalized Fees Paid to a Related Party (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Dec. 31, 2015
Capitalized Fees paid to a Related Party
Net Carrying Value	$ 190,912		$ 194,368	[1]
Amortization of capitalized fees paid to a related party	3,456	$ 3,456
Estimated amortization expense for the remainder of 2016	10,400
Estimated amortization expense for the year 2017	13,800
Estimated amortization expense for the year 2018	13,800
Estimated amortization expense for the year 2019	13,800
Estimated amortization expense for the year 2020	13,800
Estimated amortization expense for the year 2021	13,800
Estimated amortization expense thereafter	111,400
GSK
Capitalized Fees paid to a Related Party
Amortization of capitalized fees paid to a related party	$ 3,456	3,456
GSK | Long-acting beta agonist (LABA) collaboration
Capitalized Fees paid to a Related Party
Weighted Average Remaining Amortization Period	13 years 10 months 24 days
Gross Carrying Value	$ 220,000		220,000
Accumulated Amortization	(29,088)		(25,632)
Net Carrying Value	190,912		$ 194,368
Amortization of capitalized fees paid to a related party	$ 3,500	$ 3,500

[1] Condensed consolidated balance sheet as of December 31, 2015 has been derived from audited consolidated financial statements.