Acquisitions - Purchase Price Allocation (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Sep. 30, 2017	Mar. 31, 2017
Business Acquisition [Line Items]
Goodwill	$ 289,438	$ 254,760	$ 254,217
Trade Names
Business Acquisition [Line Items]
Indefinite lived intangible assets	11,100
Camira Administration Corp and Subsidiaries and Bazareno Acquisitions
Business Acquisition [Line Items]
Cash and cash equivalents	2,560
Earning assets	19,594
Other assets	3,899
Property and equipment, intangible assets and other assets, net	13,153
Goodwill	34,784
Accounts payable, deferred taxes and other liabilities	(7,349)
Total consideration	$ 66,641