Related Party Transactions - Summary of Expenses Incurred by Company (Detail) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2015	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
The Trustees of the University of Pennsylvania [Member]
Related Party Transaction [Line Items]
Total related party transaction expense	$ 5,216		$ 1,378	$ 2,921
The Trustees of the University of Pennsylvania [Member] | Manufacturing of Reagents for Sale [Member]
Related Party Transaction [Line Items]
Total related party transaction expense	80		92	143
The Trustees of the University of Pennsylvania [Member] | Research and Development Services [Member]
Related Party Transaction [Line Items]
Total related party transaction expense	$ 5,136		1,286	2,778
FoxKiser,LLP [Member]
Related Party Transaction [Line Items]
Total related party transaction expense		$ 405	2,979	2,580
FoxKiser,LLP [Member] | Research and Development Costs [Member]
Related Party Transaction [Line Items]
Total related party transaction expense		168	1,283	1,111
FoxKiser,LLP [Member] | General and Administrative [Member]
Related Party Transaction [Line Items]
Total related party transaction expense		$ 237	$ 1,696	$ 1,469