Related Party Transactions - Summary of Expenses Incurred by Company (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
The Trustees of the University of Pennsylvania [Member]
Related Party Transaction [Line Items]
Total related party transaction expense	$ 2,671	$ 185	$ 5,606	$ 1,289
The Trustees of the University of Pennsylvania [Member] | Sublicense Fees [Member]
Related Party Transaction [Line Items]
Total related party transaction expense	107		264	371
The Trustees of the University of Pennsylvania [Member] | Royalties on Sales of Reagents [Member]
Related Party Transaction [Line Items]
Total related party transaction expense	2	5	8	16
The Trustees of the University of Pennsylvania [Member] | Maintenance of Licensed Patents [Member]
Related Party Transaction [Line Items]
Total related party transaction expense	29	33	118	191
The Trustees of the University of Pennsylvania [Member] | Manufacturing of Reagents for Sale [Member]
Related Party Transaction [Line Items]
Total related party transaction expense	40	5	80	87
The Trustees of the University of Pennsylvania [Member] | Research and Development Services [Member]
Related Party Transaction [Line Items]
Total related party transaction expense	2,493	142	5,136	624
GlaxoSmithKline LLC [Member]
Related Party Transaction [Line Items]
Total related party transaction expense	165	111	743	705
GlaxoSmithKline LLC [Member] | Sublicense Fees [Member]
Related Party Transaction [Line Items]
Total related party transaction expense	107		264	371
GlaxoSmithKline LLC [Member] | Royalties on Sales of Reagents [Member]
Related Party Transaction [Line Items]
Total related party transaction expense	1	3	5	10
GlaxoSmithKline LLC [Member] | Maintenance of Licensed Patents [Member]
Related Party Transaction [Line Items]
Total related party transaction expense	$ 57	108	474	324
FoxKiser,LLP [Member]
Related Party Transaction [Line Items]
Total related party transaction expense		699	405	1,989
FoxKiser,LLP [Member] | Research and Development [Member]
Related Party Transaction [Line Items]
Total related party transaction expense		300	168	855
FoxKiser,LLP [Member] | General and Administrative [Member]
Related Party Transaction [Line Items]
Total related party transaction expense		$ 399	$ 237	$ 1,134