Term Loan - Additional Information (Detail) - 2015 Term Loan - USD ($)		9 Months Ended
	Jun. 26, 2015	Sep. 30, 2015
Debt Instrument [Line Items]
Maximum borrowing capacity	$ 50,000,000
Current borrowing capacity	30,000,000
Remaining borrowing capacity	20,000,000
Required minimum proceeds from IPO	40,000,000
Required minimum post money valuation after IPO	120,000,000
Debt drawn	$ 30,000,000
Debt maturity date		Jun. 26, 2020
Frequency of periodic payment		Quarterly
Facility fee	5.00%
First 12 months
Debt Instrument [Line Items]
Debt instrument cash interest rate percentage	12.50%
Debt instrument cash interest rate percentage	8.00%
Deferred payment in-kind interest rate	4.50%
Prepayment penalty	3.00%
After Year 1 but on or Before Year 2
Debt Instrument [Line Items]
Debt instrument cash interest rate percentage	12.50%
Debt instrument cash interest rate percentage	8.00%
Deferred payment in-kind interest rate	4.50%
Prepayment penalty	2.00%
After Year 2 but on or Before Year 3
Debt Instrument [Line Items]
Debt instrument cash interest rate percentage	12.50%
Prepayment penalty	1.00%
After Year 3 Thereafter Until Maturity
Debt Instrument [Line Items]
Prepayment penalty	0.00%
MRIdian System
Debt Instrument [Line Items]
Required minimum gross revenue from MRIdian system sales	$ 25,000,000