Debt - Additional Information (Details) - December Two Thousand Fifteen Facility - Revolving Credit Facility - Secured Debt - USD ($)	1 Months Ended	3 Months Ended
	Dec. 31, 2015	Apr. 30, 2017	Apr. 30, 2016
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity	$ 40,000,000
Debt instrument, description of variable rate basis		The December 2015 Facility is denominated in U.S. dollars and, depending on certain conditions, each borrowing is subject to a floating interest rate equal to either the prime rate plus a spread of 0.25% to 2.75% or a reserve adjusted LIBOR rate (based on one, three or six-month interest periods) plus a spread of 1.25% to 3.75%.
Line of credit facility, commitment fee percentage	0.20%
Line of credit facility, amount drawn	$ 40,000,000
Line of credit facility, interest rate	1.82%
Line of credit facility maturity date		Dec. 31, 2018
Line of credit facility, interest expense		$ 200,000	$ 200,000
London Interbank Offered Rate (LIBOR)
Debt Instrument [Line Items]
Line of credit facility, floating interest rate	1.25%
Minimum
Debt Instrument [Line Items]
Minimum deposit held as collateral for line of credit	$ 0
Minimum deposit amount with lender	$ 40,000,000
Minimum | Prime Rate
Debt Instrument [Line Items]
Line of credit facility, floating interest rate	0.25%
Minimum | London Interbank Offered Rate (LIBOR)
Debt Instrument [Line Items]
Line of credit facility, floating interest rate	1.25%
Maximum | Prime Rate
Debt Instrument [Line Items]
Line of credit facility, floating interest rate	2.75%
Maximum | London Interbank Offered Rate (LIBOR)
Debt Instrument [Line Items]
Line of credit facility, floating interest rate	3.75%