Derivative Instruments - Schedule of Interest Rate Swaps (Details) - Derivatives Not Designated as Hedging Instruments	Sep. 30, 2018 USD ($)
Tranche A
Derivative [Line Items]
Notional amount at inception (in thousands)	$ 300,000,000
Fixed interest rate	2.204%
Tranche B
Derivative [Line Items]
Notional amount at inception (in thousands)	$ 200,000,000
Fixed interest rate	2.212%
Tranche C
Derivative [Line Items]
Notional amount at inception (in thousands)	$ 400,000,000
Amortization	5.00%
Fixed interest rate	1.108%
Tranche D
Derivative [Line Items]
Notional amount at inception (in thousands)	$ 150,000,000
Fixed interest rate	1.125%
Tranche E
Derivative [Line Items]
Notional amount at inception (in thousands)	$ 250,000,000
Fixed interest rate	0.896%