Leases - Additional Disclosure (Details) $ in Thousands		1 Months Ended	3 Months Ended	12 Months Ended
	Oct. 31, 2018 USD ($)	Dec. 31, 2014 USD ($) extension_option	Mar. 31, 2015 USD ($)	Sep. 30, 2018	Sep. 30, 2019 USD ($)	Sep. 30, 2017 USD ($)	Sep. 30, 2016 USD ($)
Operating Leased Assets [Line Items]
Estimated minimum future rental payments					$ 267,886
Estimated future minimum sublease payments					12,607
Gain on early termination of sublease	$ 700
Corporate Office Lease
Operating Leased Assets [Line Items]
Initial term of lease, in years		13 years
Annual rent at lease inception		$ 2,500
Annual rent in the terminal year of lease		$ 3,900
Number of extension options | extension_option		2
Renewable term of lease, in years		5 years
Estimated minimum future rental payments					$ 38,100
Estimated future minimum sublease payments						$ 12,200	$ 12,200
Initial leased premises surrendered				15.00%
Regional Offices Sublease | Miami and Mexico City
Operating Leased Assets [Line Items]
Estimated future minimum sublease payments			$ 4,600
Regional Offices Sublease | Miami
Operating Leased Assets [Line Items]
Sublease term			9 years
Minimum
Operating Leased Assets [Line Items]
Initial term of lease, in years					3 years
Renewable term of lease, in years					3 years
Maximum
Operating Leased Assets [Line Items]
Initial term of lease, in years					10 years
Renewable term of lease, in years					5 years