Credit Facility and Convertible Debentures - Additional Information (Detail) - USD ($)			1 Months Ended	3 Months Ended		6 Months Ended
	Apr. 15, 2019	May 31, 2018	Jul. 31, 2019	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Debt Instrument [Line Items]
Repayments of lines of credit						$ 24,024,000	$ 0
Gain (loss) from covenant liability				$ (3,000,000)		(1,000,000)
Interest expense				5,682,000	$ 3,422,000	8,217,000	6,112,000
Revolving Credit Facility
Debt Instrument [Line Items]
Cash and cash equivalent threshold		$ 50,000,000
Revolving Credit Facility | Line of Credit
Debt Instrument [Line Items]
Interest expense				$ 5,700,000	2,900,000	$ 8,200,000	4,700,000
Debt instrument, interest rate, effective percentage				15.10%		15.10%
Interest paid				$ 4,600,000	$ 1,300,000	$ 6,600,000	$ 2,600,000
Credit Facility | Revolving Credit Facility | Interest Rate Application A | London Interbank Offered Rate (LIBOR)
Debt Instrument [Line Items]
Basis spread on variable rate		8.50%
Credit Facility | Revolving Credit Facility | Interest Rate Application A | London Interbank Offered Rate (LIBOR) | Minimum
Debt Instrument [Line Items]
Basis spread on variable rate		1.00%
Credit Facility | Revolving Credit Facility | Interest Rate Application B
Debt Instrument [Line Items]
Basis spread on variable rate		2.00%
Credit Facility | Revolving Credit Facility | Interest Rate Application B | Minimum
Debt Instrument [Line Items]
Basis spread on variable rate		7.50%
Credit Facility | Revolving Credit Facility | Interest Rate Application B | London Interbank Offered Rate (LIBOR)
Debt Instrument [Line Items]
Basis spread on variable rate		1.00%
Credit Facility | Revolving Credit Facility | Interest Rate Application B | Federal Funds Effective Swap Rate
Debt Instrument [Line Items]
Basis spread on variable rate		0.50%
Amended Credit Facility
Debt Instrument [Line Items]
Long-term line of credit outstanding				44,500,000		44,500,000
Cash and cash equivalent threshold		$ 50,000,000		50,000,000		50,000,000
Repayments of lines of credit	$ 24,000,000
Periodic payment, interest	$ 2,900,000
Liquidity threshold		20,000,000
Minimum aggregate appraised value plus liquidity threshold		350,000,000
Deployment threshold		40,000,000.0
Expense threshold		11,500,000.0
Unamortized discount and debt issuance costs				1,500,000		1,500,000
Long-term debt				43,100,000		43,100,000
Credit facility repayment feature		$ 500,000		$ 4,100,000		$ 4,100,000		$ 1,000,000
Amended Credit Facility | Subsequent Event
Debt Instrument [Line Items]
Extinguishment of debt, amount			$ 44,500,000
Interest expense			$ 4,100,000