Loan Sales and Variable Interest Entities - Summary of Collection Status Information for Loans Accounted for Sales (Detail) - Variable Interest Entity, Not Primary Beneficiary, Aggregated Disclosure [Member] - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Mortgage Loans On Real Estate [Line Items]
UPB of loans outstanding	$ 105,796,998	$ 91,982,335
UPB of delinquent loans:
30-89 days delinquent	729,671	614,668
90 or more days delinquent:
Not in foreclosure	171,297	142,871
In foreclosure	39,675	40,445
UPB of loans in bankruptcy	107,557	75,947
Custodial funds managed by the Company	$ 1,894,889	$ 970,328