MORTGAGE SERVICING RIGHTS - Presentation of Activity Related to MSR (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Servicing Asset at Fair Value, Amount [Roll Forward]
Fair value, beginning of period	$ 557,813	$ 580,860
Changes in valuation inputs or assumptions	(43,089)	36,674
Other changes, including realization of expected cash flows	(13,979)	(21,156)
Fair value, end of period	$ 500,745	$ 596,378