Capitalized Fees Paid to a Related Party (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014
Capitalized Fees paid to a Related Party
Net Carrying Value	$ 197,824		$ 197,824		$ 208,191	[1]
Amortization of capitalized fees paid to a related party	3,455	$ 3,233	10,367	$ 7,611
Estimated amortization expense for the remainder of 2015	3,500		3,500
Estimated amortization expense for the year 2016	13,800		13,800
Estimated amortization expense for the year 2017	13,800		13,800
Estimated amortization expense for the year 2018	13,800		13,800
Estimated amortization expense for the year 2019	13,800		13,800
Estimated amortization expense for the year 2020	13,800		13,800
Estimated amortization expense thereafter	125,300		125,300
GSK
Capitalized Fees paid to a Related Party
Amortization of capitalized fees paid to a related party	3,455	3,233	$ 10,367	7,611
GSK | Long-acting beta agonist (LABA) collaboration
Capitalized Fees paid to a Related Party
Weighted Average Remaining Amortization Period			14 years 4 months 24 days
Gross Carrying Value	220,000		$ 220,000		220,000
Accumulated Amortization	(22,176)		(22,176)		(11,809)
Net Carrying Value	197,824		197,824		$ 208,191
Amortization of capitalized fees paid to a related party	$ 3,500	$ 3,200	$ 10,400	$ 7,600

[1] Condensed consolidated balance sheet as of December 31, 2014 has been derived from audited consolidated financial statements.