Acquisitions - Purchase Price Allocation (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Sep. 30, 2017	Dec. 31, 2016
Business Acquisition [Line Items]
Goodwill	$ 288,773	$ 254,760	$ 253,585
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	4,005
Property and equipment, intangible assets and other assets, net	13,153
Goodwill	34,678
Accounts payable, deferred taxes and other liabilities	(7,349)
Total consideration	$ 66,641