Fair Value Measurements and Derivatives Instruments - Additional Information (Details) - USD ($)	9 Months Ended
	Jun. 30, 2018	Sep. 30, 2017
Interest Rate Contracts
Derivative [Line Items]
Notional amount	$ 1,560,000,000	$ 2,180,000,000
Interest Rate Swap
Derivative [Line Items]
Net deferred losses on interest rate swap net of taxes expected to be recognized over the next 12 months	$ 5,689,000