Commitments and Contingencies - Additional Information (Detail)						1 Months Ended			11 Months Ended	12 Months Ended
	Oct. 17, 2018 USD ($)	Jul. 13, 2018 USD ($)	Feb. 20, 2018 USD ($)	Oct. 10, 2017 USD ($) Trust	Oct. 09, 2017 Trust	Feb. 28, 2019 USD ($)	Oct. 31, 2018 USD ($)	Feb. 09, 2018 USD ($)	Dec. 31, 2018 USD ($) Trust	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2017 USD ($)	Sep. 30, 2017 USD ($)	Jan. 09, 2017	Dec. 31, 2016 USD ($)
Loss Contingencies [Line Items]
Iinducement fee balance									$ 11,022,000				$ 29,256,000
Number of securitization trusts related to Non Residual Trusts | Trust									3
Percentage of maximum claim amount, repurchase threshold									98.00%
Reverse loans and real estate owned repurchased from securitization pools								$ 257,100,000	$ 1,600,000,000				1,300,000,000
Fair value of repurchased reverse loans and real estate owned									9,146,956,000				10,725,232,000
Curtailment liability									$ 99,781,000				140,905,000
Leases expire through date									Nov. 30, 2026
Rent expense								1,700,000	$ 16,000,000				18,600,000
Litigation settlement amount	$ 258,000	$ 2,950,000
Percentage of equity of acquirer of Walter Energy core assets for which a prospect of payment of unsecured claims exists															1.00%
Walter Energy tax year under audit									2009
Variable Interest Entity, Primary Beneficiary [Member]
Loss Contingencies [Line Items]
Fair value of repurchased reverse loans and real estate owned									$ 324,934,000				301,435,000
Non-Residual Trusts [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Loss Contingencies [Line Items]
Number of securitization trusts with reimbursement obligations | Trust				2	7
Fair value of repurchased reverse loans and real estate owned									$ 117,410,000				301,435,000
Mandatory Clean-up Call Obligation [Member]
Loss Contingencies [Line Items]
Mandatory cleanup calls required when loan pool falls to percent of original principal balance									10.00%
Obligation To Reimburse Third Party As Credit Enhancement To Trusts [Member]
Loss Contingencies [Line Items]
Aggregate number of securitization trusts with reimbursement obligations | Trust				11	11
Obligation to reimburse amounts drawn on LOCs in excess of threshold									$ 17,000,000
Draws on LOCs made by counterparty									11,900,000
Additional Borrowing Capacity Floating Rate Reverse Mortgage Loans [Member] | Reverse Mortgage [Member]
Loss Contingencies [Line Items]
Commitments									894,200,000
Borrowing capacity eligible to be drawn by borrowers at December 31, 2018									1,000,000,000
Additional Borrowing Capacity Fixed Rate Reverse Mortgage Loans [Member] | Reverse Mortgage [Member]
Loss Contingencies [Line Items]
Commitments									57,600,000
Commitment To Fund Protective Advances [Member] | Reverse Mortgage [Member]
Loss Contingencies [Line Items]
Commitments									22,400,000
Short Term Commitments To Lend [Member] | Originations [Member]
Loss Contingencies [Line Items]
Commitments									1,300,000,000
Commitment to Purchase Loans [Member] | Originations [Member]
Loss Contingencies [Line Items]
Commitments to purchase loans									3,100,000
Commitment To Sell Securities [Member] | Originations [Member]
Loss Contingencies [Line Items]
Commitments									2,300,000,000
Commitment to Purchase Mortgage Backed Securities [Member] | Originations [Member]
Loss Contingencies [Line Items]
Commitments									677,500,000
Repurchased Reverse Loans And Real Estate Owned [Member]
Loss Contingencies [Line Items]
Repurchased reverse loans and real estate owned									1,100,000,000
Fair value of repurchased reverse loans and real estate owned									1,000,000,000
Repurchased Reverse Loans And Real Estate Owned [Member] | Commitment to Purchase Loans [Member]
Loss Contingencies [Line Items]
Commitments to purchase loans									165,100,000
Representations And Warranties [Member] | Commitment to Purchase Loans [Member] | Originations [Member]
Loss Contingencies [Line Items]
Loss contingency accrual								16,487,000	12,747,000				$ 16,792,000			$ 22,094,000
Representations And Warranties [Member] | Commitment to Repurchase Loans [Member] | Originations [Member]
Loss Contingencies [Line Items]
Commitments									67,800,000,000
Curtailment Obligation Liability [Member]
Loss Contingencies [Line Items]
Loss contingency recorded in current period								$ 400,000	(7,400,000)
Curtailment Obligation Liability [Member] | Reverse Mortgage [Member]
Loss Contingencies [Line Items]
Curtailment liability									68,700,000
Aggregate estimated amount of reasonably possible losses in excess of recorded liability									61,800,000
Curtailment Obligation Liability [Member] | Originations [Member]
Loss Contingencies [Line Items]
Curtailment liability									31,100,000
Pending Litigation [Member]
Loss Contingencies [Line Items]
Loss contingency accrual									19,000,000
Pending Litigation [Member] | Minimum [Member]
Loss Contingencies [Line Items]
Aggregate estimated amount of reasonably possible losses in excess of recorded liability									0
Pending Litigation [Member] | Maximum [Member]
Loss Contingencies [Line Items]
Aggregate estimated amount of reasonably possible losses in excess of recorded liability									12,000,000
Officers [Member] | Retention Bonus [Member]
Loss Contingencies [Line Items]
Total retention bonus														$ 2,800,000
Chief Executive Officer [Member] | Retention Bonus [Member]
Loss Contingencies [Line Items]
Retention bonus forfeited			$ 1,300,000
Management [Member] | Deferred Bonus [Member]
Loss Contingencies [Line Items]
Total amount paid under agreement or plan							$ 5,900,000
Clean-Up Call Agreement Transactions [Member]
Loss Contingencies [Line Items]
Payment of inducement fee				$ 36,500,000
Right to receive reimbursement for outstanding advances									2,700,000
Number of securitization trusts related to Non Residual Trusts | Trust				8
Obligation to reimburse amounts drawn on LOCs in excess of threshold									$ 17,000,000
Clean-Up Call Agreement Transactions [Member] | Maximum [Member]
Loss Contingencies [Line Items]
Right to receive reimbursement for outstanding advances				$ 6,400,000
Forecast [Member]
Loss Contingencies [Line Items]
Reverse loans and real estate owned repurchased from securitization pools										$ 643,700,000	$ 1,200,000,000	$ 2,000,000,000
Subsequent Event [Member] | Management [Member] | Incentive Bonus [Member]
Loss Contingencies [Line Items]
Total amount paid under agreement or plan						$ 2,500,000