Credit Facilities - Additional Information (Details) - USD ($)	Feb. 27, 2018	Jun. 30, 2019
Line of Credit Facility [Line Items]
Line of credit, available borrowings	$ 200,000,000.0
Current borrowing capacity	$ 50,000,000.0
Outstanding borrowings		$ 0
Base Rate
Line of Credit Facility [Line Items]
Basis Spread on Variable Rate	0.50%
London Interbank Offered Rate (LIBOR)
Line of Credit Facility [Line Items]
Basis Spread on Variable Rate	1.00%
Minimum | Base Rate
Line of Credit Facility [Line Items]
Basis Spread on Variable Rate	0.25%
Minimum | London Interbank Offered Rate (LIBOR)
Line of Credit Facility [Line Items]
Basis Spread on Variable Rate	1.25%
Maximum | Base Rate
Line of Credit Facility [Line Items]
Basis Spread on Variable Rate	0.75%
Maximum | London Interbank Offered Rate (LIBOR)
Line of Credit Facility [Line Items]
Basis Spread on Variable Rate	1.75%