Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2014

Property Plant and Equipment Estimated Useful Lives

Property, plant and equipment are recorded at cost and are amortized over their estimated useful lives using the straight-line method based on the following rates:

Asset	Rate
Research equipment	5 years
Office furniture and equipment	5 years
Computer equipment	3 years
Leasehold improvements	Over the lesser of lease term or estimated useful life

Revenue Recognized From Collaborations

The following table is a summary of the revenue recognized from the Company’s collaborations for each of the years ended December 31, 2014, 2013 and 2012.

	Year Ended December 31,
	2014		2013		2012
uniQure:
Milestone payment	$	14	$	531	$	198
Teva:
Recognition of upfront payment		12,255		13,143		927
Research funding		333		630		—
Genentech:
Recognition of upfront payment		3,603		3,300		3,431
Research funding		4,248		4,514		3,517
Milestone payment		7,913		5,062		—
Merck:
Recognition of initial payment		—		—		1,060
Option fee		—		—		2,060
Research funding		—		—		2,442
Genome BC:
Research funding		—		172		665
Total collaboration revenue	$	28,366	$	27,352	$	14,300

Collaboration Research And Development Revenue [Member]

Revenue Recognized From Collaborations

Collaborators whose collaboration research and development revenue accounted for 10% or more of total revenues were as follows:

	Year ended December 31,
	2014		2013		2012
Genentech	$	15,764	$	12,876	$	6,948
Merck		—		—		5,562
Teva		12,588		13,773		—