Leases - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
	Mar. 31, 2019	Mar. 31, 2019	Mar. 31, 2020	Oct. 01, 2019
Lessee, Lease, Description [Line Items]
Right-of-use asset			$ 222,653
Operating lease liabilities			$ 231,045
Lease and rental expense	$ 10,300	$ 20,300
Accounting Standards Update 2016-02
Lessee, Lease, Description [Line Items]
Right-of-use asset				$ 231,300
Operating lease liabilities				231,300
Accrued and prepaid rent reclassified				6,500
Deferred rent credits and other liabilities reclassified				$ 2,500