Servicing of Residential Loans - Schedule of Servicing Rights Carried at Fair Value (Detail) - USD ($) $ in Thousands	1 Months Ended	11 Months Ended	12 Months Ended
	Feb. 09, 2018	Dec. 31, 2018	Dec. 31, 2017
Servicing Asset at Fair Value, Amount [Roll Forward]
Balance at beginning of the period	$ 714,774	$ 688,466	$ 949,593
Sales	(105,457)	(194,573)	(117,470)
Other	(7)	(88)	0
Change in fair value due to:
Changes in valuation inputs or other assumptions	78,132	2,195	(134,573)
Other changes in fair value	(13,469)	(99,202)	(131,673)
Total change in fair value	64,663	(97,007)	(266,246)
Balance at end of the period	688,466	563,144	714,774
Servicing Rights Capitalized Upon Sales of Loans [Member]
Servicing Asset at Fair Value, Amount [Roll Forward]
Servicing rights acquired, purchased or capitalized	14,493	166,203	148,227
Purchases [Member]
Servicing Asset at Fair Value, Amount [Roll Forward]
Servicing rights acquired, purchased or capitalized	$ 0	$ 143	$ 670