Description of Operations and Summary of Significant Accounting Policies - Description of Operations and Variable Interest Entity (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Description of Operations and Summary of Significant Accounting Policies
Cash balance	$ 141,952		$ 141,952		$ 62,417	[1]
Net revenue	64,107	$ 67,086	119,290	$ 119,466
GSK
Description of Operations and Summary of Significant Accounting Policies
Net revenue	64,107	67,086	$ 119,290	119,466
Long-Acting Beta2 Agonist (LABA) Collaboration | GSK
Description of Operations and Summary of Significant Accounting Policies
Percentage of economic interest in any future payments made under the agreements			15.00%
Long-Acting Beta2 Agonist (LABA) Collaboration | GSK | RELVAR/BREO
Description of Operations and Summary of Significant Accounting Policies
Royalty rate for first level of annual global net sales (as a percent)			15.00%
Annual global sales level used to determine royalty rate			$ 3,000,000
Royalty rate for sales above first level of annual global net sales (as a percent)			5.00%
Long-Acting Beta2 Agonist (LABA) Collaboration | GSK | ANORO | Minimum
Description of Operations and Summary of Significant Accounting Policies
Royalty rate for combination products (as a percent)			6.50%
Long-Acting Beta2 Agonist (LABA) Collaboration | GSK | ANORO | Maximum
Description of Operations and Summary of Significant Accounting Policies
Royalty rate for combination products (as a percent)			10.00%
TRC
Description of Operations and Summary of Significant Accounting Policies
Cash balance	13,800		$ 13,800
TRC | TRELEGY
Description of Operations and Summary of Significant Accounting Policies
Net revenue	9,800	$ 2,400	17,200	$ 3,300
TRC | Collaborative arrangement
Description of Operations and Summary of Significant Accounting Policies
Related-party receivables	$ 9,800		$ 9,800		$ 6,400

[1] Condensed consolidated balance sheet as of December 31, 2018 has been derived from audited consolidated financial statements.