Line of Credit (Details) - USD ($)		1 Months Ended		9 Months Ended
	Jun. 13, 2016	Oct. 31, 2017	Jul. 31, 2017	Sep. 30, 2018	Sep. 30, 2017	Oct. 18, 2018
Line of Credit Facility [Line Items]
Credit facility principal payment				$ 30,000,000	$ 0
Revolving Credit Facility
Line of Credit Facility [Line Items]
Credit facility term of agreement	5 years
Credit facility maximum borrowing capacity	$ 300,000,000
Credit facility stated percentage	0.00%
Credit facility accordion feature, increase limit	$ 100,000,000
Credit facility borrowings			$ 40,000,000
Credit facility principal payment		$ 10,000,000		$ 30,000,000
Revolving Credit Facility | Subsequent Event
Line of Credit Facility [Line Items]
Credit facility remaining borrowing capacity						$ 300,000,000
Revolving Credit Facility | London Interbank Offered Rate (LIBOR)
Line of Credit Facility [Line Items]
Credit facility variable interest rate basis spread	1.00%
Revolving Credit Facility | Federal Funds Rate
Line of Credit Facility [Line Items]
Credit facility variable interest rate basis spread	0.50%
Revolving Credit Facility | Minimum
Line of Credit Facility [Line Items]
Credit facility commitment fee per annum on daily unused portion	0.15%
Revolving Credit Facility | Minimum | Lender's Base Rate Plus Market Spread
Line of Credit Facility [Line Items]
Credit facility variable interest rate basis spread	0.25%
Revolving Credit Facility | Minimum | London Interbank Offered Rate (LIBOR)
Line of Credit Facility [Line Items]
Credit facility variable interest rate basis spread	1.25%
Revolving Credit Facility | Maximum
Line of Credit Facility [Line Items]
Credit facility commitment fee per annum on daily unused portion	0.30%
Revolving Credit Facility | Maximum | Lender's Base Rate Plus Market Spread
Line of Credit Facility [Line Items]
Credit facility variable interest rate basis spread	1.00%
Revolving Credit Facility | Maximum | London Interbank Offered Rate (LIBOR)
Line of Credit Facility [Line Items]
Credit facility variable interest rate basis spread	2.00%