COMMITMENTS AND CONTINGENCIES - Narrative (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Loss Contingencies [Line Items]
Representation and warranties		$ 36,500
Residential mortgage loan repurchase liability	[1]	1,787,314	$ 1,452,005
Loans of unfunded and available revolving credit privileges		289,065	51,575
Rent expense, net of sublease income		26,100	13,500	$ 10,300
Sublease rentals		1,200
Consumer Portfolio Segment
Loss Contingencies [Line Items]
Loans of unfunded and available revolving credit privileges		507,291	$ 685,575	$ 827,545
New Penn
Loss Contingencies [Line Items]
Committed to fund		10,700,000
Consumer Loan SPVs | Consumer Portfolio Segment | Unfunded Loan Commitment
Loss Contingencies [Line Items]
Loans of unfunded and available revolving credit privileges		244,100
Genesis Acquisition
Loss Contingencies [Line Items]
Committed to fund		$ 539,400

[1] See Note 6 for details.