SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Schedule of Accretion and Other Amortization (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Accretion of discount and other amortization:
Accretion of servicer advance investment and receivable interest income	$ 542,983	$ 364,350	$ 352,316
Accretion of excess mortgage servicing rights income	103,053	150,141	134,565
Accretion of net discount on securities and loans	398,213	253,243	65,925
Amortization of deferred financing costs	(12,076)	(18,326)	(26,036)
Amortization of discount on notes and bonds payable	(789)	(1,476)	(1,472)
Accretion and other amortization	$ 1,031,384	$ 747,932	$ 525,298