ACQUISITIONS, Acquisition Related Expenses (Details) - Business Combination, Acquisition Related Costs - U.S. Private Client Services of Deutsche WM - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
	Mar. 31, 2016	Mar. 31, 2016
Business Acquisition [Line Items]
Total acquisition-related expenses	$ 6,015	$ 7,887
Unrealized loss in fair value of equity securities purchased to satisfy certain deferred compensation obligations to be assumed at closing
Business Acquisition [Line Items]
Total acquisition-related expenses	3,165	3,319
Legal
Business Acquisition [Line Items]
Total acquisition-related expenses	422	1,923
Information systems integration costs
Business Acquisition [Line Items]
Total acquisition-related expenses	1,655	1,655
Travel and all other
Business Acquisition [Line Items]
Total acquisition-related expenses	$ 773	$ 990