SECURITIES - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Investments, Debt and Equity Securities [Abstract]
Residential Investment securities sold, carrying value	$ 10,500.0	$ 463.4
Residential Investment securities sold, net realized gain (loss)	$ (92.5)	$ 13.0