Collaboration and License Agreements - Summary of Collaboration Expenses (Details) - USD ($) $ in Thousands		3 Months Ended								12 Months Ended
	Jul. 01, 2017	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Collaboration revenues:
Product revenue		$ 13,369	$ 10,890	$ 19,140	$ 23,404	$ 15,817	$ 23,339	$ 20,692	$ 14,800	$ 66,803	$ 74,648	$ 48,503
Research and development revenue:
Commercial milestone										10,000		20,000
Recognition of upfront payments										55,015	28,351	9,014
Research and development services and external costs										7,064	6,620	12,133
Total research and development revenue										72,079	34,971	41,147
Total collaboration revenue		$ 64,608	$ 24,090	$ 23,570	$ 26,614	$ 34,195	$ 29,144	$ 26,430	$ 19,850	138,882	109,619	89,650
Operating expenses:
Research and development expense										73,952	58,946	3,031
General and administrative expense										19,661	3,673	1,513
Less: net amount recovered from collaborators										(29,155)	(27,770)
Total operating expenses										64,458	34,849	4,544
2003 Sandoz Collaboration Agreement
Collaboration revenues:
Product revenue										313	0	5,063
Research and development revenue:
Commercial milestone										0		0
Recognition of upfront payments										0	0	0
Research and development services and external costs										2,856	345	789
Total research and development revenue										2,856	345	789
Total collaboration revenue										3,169	345	5,852
Operating expenses:
Research and development expense										1,958	692	324
General and administrative expense										15,426	7	344
Less: net amount recovered from collaborators										0	0
Total operating expenses										17,384	699	668
2006 Sandoz Collaboration Agreement
Collaboration revenues:
Product revenue										66,490	74,648	43,440
Research and development revenue:
Commercial milestone	$ 10,000									10,000		20,000
Recognition of upfront payments										0	0	0
Research and development services and external costs										2,142	2,545	2,861
Total research and development revenue										12,142	2,545	22,861
Total collaboration revenue										78,632	77,193	66,301
Operating expenses:
Research and development expense										1,766	1,911	856
General and administrative expense										494	470	206
Less: net amount recovered from collaborators										0	0
Total operating expenses										2,260	2,381	1,062
Mylan Collaboration Agreement
Collaboration revenues:
Product revenue										0	0
Research and development revenue:
Commercial milestone										0
Recognition of upfront payments										5,015	6,368
Research and development services and external costs										0	0
Total research and development revenue										5,015	6,368
Total collaboration revenue										5,015	6,368
Operating expenses:
Research and development expense										62,049	55,147
General and administrative expense										3,617	3,009
Less: net amount recovered from collaborators										(25,835)	(27,770)
Total operating expenses										39,831	30,386
CSL License Agreement
Collaboration revenues:
Product revenue										0
Research and development revenue:
Commercial milestone										0
Recognition of upfront payments										50,000
Research and development services and external costs										2,066
Total research and development revenue										52,066
Total collaboration revenue										52,066
Operating expenses:
Research and development expense										8,179
General and administrative expense										124
Less: net amount recovered from collaborators										(3,320)
Total operating expenses										$ 4,983
Baxalta Collaboration Agreement
Collaboration revenues:
Product revenue											0	0
Research and development revenue:
Commercial milestone												0
Recognition of upfront payments											21,983	9,014
Research and development services and external costs											3,730	8,483
Total research and development revenue											25,713	17,497
Total collaboration revenue											25,713	17,497
Operating expenses:
Research and development expense											1,196	1,851
General and administrative expense											187	963
Less: net amount recovered from collaborators											0
Total operating expenses											$ 1,383	$ 2,814