Property and Equipment (Details) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2015 USD ($)	Dec. 31, 2013 ft²	Dec. 31, 2014 USD ($)
Property and Equipment
Property and Equipment, gross	$ 125,246		$ 116,464
Less accumulated depreciation and amortization	(42,060)		(34,674)
Property and Equipment, net	83,186		81,790	[1]
Area of laboratory and office building on lease (in square feet) | ft²		190,000
Term of lease		15 years
Minimum monthly lease rental	$ 500
Initial term of lease over which minimum lease rent is required to be payable	10 years
Last term of lease	5 years
Letter of credit for posted for lease facility	$ 15,000
Restricted investments related to direct financing lease	14,100		14,500
Office Equipment
Property and Equipment
Property and Equipment, gross	6,288		6,090
Laboratory Equipment
Property and Equipment
Property and Equipment, gross	29,334		26,800
Computer Equipment
Property and Equipment
Property and Equipment, gross	21,719		18,648
Building And Leasehold Improvements
Property and Equipment
Property and Equipment, gross	$ 67,905		$ 64,926

[1] The condensed consolidated balance sheet at December 31, 2014 has been derived from the audited financial statements at that date.