MORTGAGE SERVICING RIGHTS - Presentation of Activity Related to MSR (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Servicing Asset at Fair Value, Amount [Roll Forward]
Fair value, beginning of period	$ 580,860	$ 652,216
Sales	0	(33)
Other	(4)	(27)
Changes in valuation inputs or assumptions	56,721	(4,629)
Other changes, including realization of expected cash flows	(79,764)	(66,667)
Fair value, end of period	$ 557,813	$ 580,860