Fair Value Measurements - Additional Information (Detail)	6 Months Ended	12 Months Ended
	Jun. 30, 2016 USD ($) CommercialTest shares	Dec. 31, 2015 USD ($) shares	Jun. 15, 2016 shares
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Transfers between Level 1, Level 2 and Level 3 categories during the periods | $	$ 0	$ 0
Warrants outstanding			1,002,507
Fair Value Measured Using - (Level 3) [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Warrants outstanding	2,978,087
ImmuMetrix, Inc. [Member] | Contingent consideration [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Contingent obligation to issue common stock	227,845	227,845
Milestone description	The issuance will occur if the Company completes 2,500 commercial tests involving the measurement of dd-cfDNA in organ transplant recipients in the United States by June 10, 2020.
Number of commercial tests involving the measurement of cfDNA to be completed | CommercialTest	2,500
Probability of the achievement	65.00%