Fair Value - Additional Information (Detail) $ in Thousands	1 Months Ended	11 Months Ended	12 Months Ended
	Feb. 09, 2018 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Servicing rights at fair value transferred from level 3 to 2		$ 14,565		$ 34,847
Real estate owned, net		75,567	$ 75,567	116,553
Loans in process of foreclosure		349,000	$ 349,000	489,000
Concentrations threshold			5.00%
Real estate owned expenses	$ 100	(38,600)		7,400
Real estate owned, lower of cost or fair value adjustment	$ 700	3,900		5,300
Servicing Rights Carried at Fair Value [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Servicing rights at fair value transferred from level 3 to 2		14,565		34,847
Mortgage Loans Related To Non-Residual Trusts [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Servicing rights at fair value transferred from level 3 to 2		0		0
Number of days delinquent			90 days
Loans 90 days or more past due, fair value		1,100	$ 1,100	0
Loans 90 days or more past due, unpaid principal balance		9,900	$ 9,900	22,200
Mortgage Loans Related To Residual Trusts [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Servicing rights at fair value transferred from level 3 to 2		0
Mortgage Loans Held for Sale [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Servicing rights at fair value transferred from level 3 to 2		0		0
Number of days delinquent			90 days
Loans 90 days or more past due, unpaid principal balance		5,600	$ 5,600	10,100
Charged-off Loans [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Servicing rights at fair value transferred from level 3 to 2		0		0
Number of days delinquent			90 days
Servicing Segment [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Real estate owned, net		7,800	$ 7,800	13,700
Reverse Mortgage Segment [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Real estate owned, net		67,300	67,300	101,800
Corporate and Other Non-Reportable Segment [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Real estate owned, net		$ 500	$ 500	$ 1,100
Loss Severity [Member] | Mortgage Loans Related To Non-Residual Trusts [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans 90 days or more past due, loss severity		0.89	0.89	1