Derivative Instruments and Hedging Activities - Additional Information (Details) - USD ($)			12 Months Ended
	Aug. 31, 2017	Sep. 30, 2016	Dec. 31, 2017
Derivative [Line Items]
Net amount of realized gains and losses from hedge agreements			$ 700,000
Interest Rate Swap | Cash Flow Hedging | Designated as Hedging Instrument
Derivative [Line Items]
Aggregate notional amount	$ 25,000,000	$ 100,000,000
Derivative, Fixed Interest Rate	1.8475%
Beginning date of transaction	Aug. 31, 2018	Jan. 31, 2018
Derivative, maturity date	Aug. 31, 2023	Jan. 31, 2023