Liability Related to Sale of Future Royalties (Details) - USD ($) $ in Thousands	3 Months Ended														6 Months Ended		12 Months Ended					36 Months Ended
	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, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2017	Dec. 31, 2016	Jun. 30, 2016	Dec. 31, 2015	Jun. 30, 2015	Dec. 31, 2017
Liability Related to Sale of Future Royalties
Royalty revenue									$ 195			$ 5,099	$ 4,625	$ 4,166		$ 195			$ 195		$ 13,867
Proceeds from sale of future royalties - net																					194,135
Transaction costs for royalty agreements																					5,865
Roll forward
Proceeds from sale of future royalties - net																					194,135
Non-cash Kadcyla royalty revenue	$ (7,587)	$ (6,503)	$ (6,439)	$ (7,613)	$ (6,710)	$ (6,184)	$ (5,944)	$ (7,380)	(6,291)	$ (5,684)	$ (5,484)				$ (12,894)	(11,975)	$ (28,142)	$ (26,218)	(25,299)		(5,484)
Non-cash interest expense on liability related to sale of future royalties and convertible senior notes	3,221	$ 3,385	$ 3,501	3,575	3,647	$ 5,018	$ 4,956	$ 4,972	$ 5,059	$ 5,143	$ 5,437				8,665	$ 10,202	13,682	18,593	$ 20,130		$ 5,437
Kadcyla
Liability Related to Sale of Future Royalties
Percentage of royalty payments if applicable threshold is met																				85.00%
Kadcyla | IRH
Liability Related to Sale of Future Royalties
Percentage of royalty payments																				100.00%
Royalty revenue																				$ 235,000
Royalties on net sales of Kadcyla when royalties to the purchaser reach a specified milestone																				$ 260,000
Percentage of royalty payments if applicable threshold is met																				15.00%
Proceeds from sale of future royalties - net																				$ 200,000		$ 194,135
Transaction costs for royalty agreements																				5,900
Roll forward
Liability related to sale of future royalties, net — beginning balance				$ 184,328													184,328
Proceeds from sale of future royalties - net																				$ 200,000		194,135
Non-cash Kadcyla royalty revenue																	(28,142)					(71,819)
Non-cash interest expense on liability related to sale of future royalties and convertible senior notes																	13,227					47,097
Liability related to sale of future royalties, net — ending balance	$ 169,413				$ 184,328										$ 184,328		$ 169,413	$ 184,328				$ 169,413
Effective annual interest rate																				7.70%