Indebtedness - Additional Information (Detail)		1 Months Ended	3 Months Ended	9 Months Ended
		Jul. 31, 2017 USD ($)	Sep. 30, 2017 USD ($) Loan	Sep. 30, 2017 USD ($) Loan	Sep. 30, 2016 USD ($)	Dec. 31, 2016 USD ($)
Debt Instrument [Line Items]
Repayment of outstanding balance				$ 15,081,000	$ 5,076,000
Net proceeds from issuance of debt				29,620,000
Revolving line-of-credit outstanding balance			$ 37,741,000	$ 37,741,000
Number of loans outstanding | Loan			2	2
Total indebtedness of unpaid principal balance			$ 1,300,000	$ 1,300,000
Interest expense related to outstanding loans			800,000	1,200,000
Revolving Loan [Member]
Debt Instrument [Line Items]
Revolving line-of-credit outstanding balance	[1]		1,026,000	1,026,000
July 2017 Term Loan [Member]
Debt Instrument [Line Items]
Net proceeds from issuance of debt				29,100,000
Long-term debt			30,000,000	30,000,000
Debt issuance costs			1,100,000	1,100,000
June 2015 Term Loan [Member]
Debt Instrument [Line Items]
Repayment of outstanding balance				9,200,000
Long-term debt						$ 15,000,000
Loan One [Member]
Debt Instrument [Line Items]
Revolving line-of-credit outstanding balance			800,000	800,000
Loan Two [Member]
Debt Instrument [Line Items]
Revolving line-of-credit outstanding balance			$ 500,000	$ 500,000
MidCap Financial Amended and Restated Credit and Security Agreement [Member] | July 2017 Term Loan [Member]
Debt Instrument [Line Items]
Current borrowing capacity		$ 60,000,000
Credit agreement interest rate per annum		6.25%
Variable interest rate description		one-month London Interbank Offered Rate
Origination fee, percentage		0.50%
Final payment fee, percentage		2.00%
Monthly principal payments commencement date		Jul. 01, 2018
Periodic principal payment frequency		monthly
Monthly principal payments		$ 800,000
Credit facility maturity date		2021-07
Debt instrument prepayment fee percent within twelve months				3.00%
Debt instrument prepayment fee percent on or after twelve months and within twenty four months				2.00%
Debt instrument prepayment fee percent on or after twenty four months				1.00%
Percentage of minimum amount of cash and/or cash equivalents on outstanding principal amounts				75.00%
Midcap Financial Revolving Credit and Security Agreement [Member] | Revolving Loan [Member]
Debt Instrument [Line Items]
Current borrowing capacity		$ 40,000,000
Credit agreement interest rate per annum		3.95%
Variable interest rate description				one-month LIBOR
Origination fee, percentage		0.50%
Credit facility maturity date		2021-07
Percentage of minimum amount of cash and/or cash equivalents on outstanding principal amounts				75.00%
Line of credit facility additional tranche that may be increased		$ 20,000,000
Origination fee		$ 200,000
Mortgage Loans [Member]
Debt Instrument [Line Items]
Credit agreement interest rate per annum			4.75%	4.75%
Credit facility maturity date				2027-02
Revolving line-of-credit outstanding balance	[1]		$ 1,307,000	$ 1,307,000

[1] Includes interest