MORTGAGE SERVICING RIGHTS - MSR Activity Rollforward (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Servicing Asset at Fair Value, Amount [Roll Forward]
Fair value, beginning of period	$ 544,562	$ 100,895
Purchases	421,012	0
Changes in valuation inputs or assumptions	158,963	27,673
Other changes, including realization of expected cash flows	(15,600)	(15,488)
Fair value, end of period	$ 1,108,937	$ 113,080