This is the sum of principal amount outstanding for both securitized and unsecuritized loans of all types.

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MORTGAGE SERVICING RIGHTS - Schedule of Activity Related to Capitalized MSRs (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017
Mortgage Servicing Rights
Beginning balance	$ 670,146
Ending balance	718,799	$ 670,146
Servicing portfolio loans unpaid principal balance	93,225,169	85,689,262	$ 91,754,499	$ 89,897,025	$ 87,691,682	$ 80,485,634	$ 77,820,741	$ 75,836,280	$ 74,309,991
MSRs
Mortgage Servicing Rights
Beginning balance	670,146	634,756
Additions, following the sale of loan	206,885	176,565
Purchases		5,265
Amortization	(137,792)	(131,739)
Pre-payments and write-offs	(20,440)	(14,701)
Ending balance	$ 718,799	670,146
Acquired Portfolio, Compensation on Loan Held for Investment \| MSRs
Mortgage Servicing Rights
Purchases		$ 3,500