Nature of Business and Plan of Operations (Details) - USD ($) $ in Thousands	1 Months Ended	3 Months Ended														6 Months Ended		12 Months Ended
	Jan. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	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	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Jun. 30, 2016	Jan. 02, 2018	Jun. 30, 2015
Net loss																$ (78,883)		$ (168,843)	$ (96,012)		$ (144,817)
Accumulated deficit		$ (1,183,335)				$ (1,028,582)												(1,183,335)	(1,028,582)			$ (1,014,492)
Total revenues		13,416	$ 10,928	$ 9,287	$ 19,815	39,448	$ 8,480	$ 39,020	$ 28,499	$ 13,846	$ 7,660	$ 7,408	$ 19,714	$ 18,029	$ 14,851	21,506	$ 32,880	53,446	115,447	$ 48,628	60,002
Cash and cash equivalents		$ 262,252				$ 267,107				$ 159,964		$ 245,026				159,964		$ 262,252	267,107	$ 159,964	245,026	$ 267,107	$ 278,109
Number of months Capital resources meets capital expenditures																		12 months
Non Cash Royalty Revenue Related To Sale of Future Royalties																$ 12,894		$ 32,154	$ 28,142		$ 25,299
Product
Total revenues																		$ 0
OMERS | Subsequent event | Kadcyla
Non Cash Royalty Revenue Related To Sale of Future Royalties	$ 65,200