Summary of Significant Accounting Policies - Revenue (Details) € in Millions	1 Months Ended	3 Months Ended		12 Months Ended
	May 31, 2013 item	Sep. 30, 2016 USD ($) item	Sep. 30, 2015 USD ($)	Jun. 30, 2016 EUR (€)	Dec. 31, 2011 item	Dec. 31, 2000 item	Jun. 30, 2016 USD ($)
Summary of Significant Accounting Policies
Prepaid expense | $		$ 7,481,000					$ 4,881,000
Number of types of licensing and development agreements with collaborative partners		2
Difference between the full cost to manufacture and amounts received from collaborators for preclinical and clinical materials | $		$ 0	$ 7,000,000
Number of types of milestone payments under collaborative arrangements		3
Number of quarters in arrear for revenue recognition		1
Minimum
Summary of Significant Accounting Policies
Period to earn royalty payments		10 years
Maximum
Summary of Significant Accounting Policies
Period to earn royalty payments		12 years
Kadcyla | Minimum
Summary of Significant Accounting Policies
Period to earn royalty payments		10 years
Kadcyla | Maximum
Summary of Significant Accounting Policies
Period to earn royalty payments		12 years
Amgen
Summary of Significant Accounting Policies
Number of single-target licenses	1	2				3
Amgen | Oxford BioTherapeutics Ltd Member
Summary of Significant Accounting Policies
Number of single-target licenses		1
Bayer
Summary of Significant Accounting Policies
Number of single-target licenses		1
Biotest
Summary of Significant Accounting Policies
Number of single-target licenses		1
CytomX
Summary of Significant Accounting Policies
Number of single-target licenses		1
Lilly
Summary of Significant Accounting Policies
Number of single-target licenses		3			3
Novartis
Summary of Significant Accounting Policies
Number of single-target licenses		5
Number of licenses to two related targets		1
Number of related targets		2
Roche
Summary of Significant Accounting Policies
Number of single-target licenses		5
Sanofi
Summary of Significant Accounting Policies
Amount paid to continue product development | €				€ 1.6
Prepaid expense | $							44,000
Potential milestone payments to be paid | $							$ 258,000
Number of single-target licenses		1
Number of licenses to multiple individual targets		1
Takeda
Summary of Significant Accounting Policies
Number of single-target licenses		1