Commitments and Contingencies - Additional Information (Detail)	3 Months Ended	6 Months Ended
	Jun. 30, 2017 USD ($)	Jun. 30, 2017 USD ($) Trust	Jun. 30, 2016 USD ($)	Jan. 09, 2017	Dec. 31, 2016 USD ($)
Loss Contingencies [Line Items]
Payment made for mandatory clean-up call obligations		$ 66,422,000	$ 52,017,000
Percentage of maximum claim amount, repurchase threshold	98.00%	98.00%
Reverse loans and real estate owned repurchased from securitization pools		$ 510,000,000	$ 259,500,000
Repurchased reverse loans and real estate owned held, fair value	$ 11,905,869,000	$ 11,905,869,000			$ 12,416,542,000
Period Of Walter Energy Consolidated Group Tax Liability		2009 and prior tax years
Tax separation agreement date		Apr. 17, 2009
Period Of Walter Energy Proof Of Claim		August 31, 1983 through May 31, 1994
Walter Energy Federal Income Tax Years Under Audit		years ended May 31, 2000 through December 31, 2008
Walter Energy Additional Federal Income Tax Years under Audit		2009 through 2013 tax years
Percentage Of Equity Of Acquirer Of Walter Energy Core Assets Prospect Of Payment Exists				1.00%
Walter Energy Tax Year Under Audit		2009
Pending Litigation
Loss Contingencies [Line Items]
Loss contingency accrual	36,000,000	$ 36,000,000
Pending Litigation | Maximum
Loss Contingencies [Line Items]
Aggregate estimated amount of reasonably possible losses in excess of recorded liability	14,000,000	14,000,000
Pending Litigation | Minimum
Loss Contingencies [Line Items]
Aggregate estimated amount of reasonably possible losses in excess of recorded liability	0	0
Repurchased Reverse Loans And Real Estate Owned
Loss Contingencies [Line Items]
Repurchased reverse loans and real estate owned held, outstanding loan balance	625,100,000	625,100,000
Repurchased reverse loans and real estate owned held, fair value	599,300,000	599,300,000
Commitment to Purchase Loans | Repurchased Reverse Loans And Real Estate Owned
Loss Contingencies [Line Items]
Commitments to purchase loans	110,000,000	110,000,000
Reverse Mortgage | Curtailment Obligation Liability
Loss Contingencies [Line Items]
Loss contingency accrual	100,300,000	100,300,000
Loss contingency recorded in current period		1,200,000
Aggregate estimated amount of reasonably possible losses in excess of recorded liability	150,600,000	150,600,000
Reverse Mortgage | Additional Borrowing Capacity Floating Rate Reverse Loans
Loss Contingencies [Line Items]
Commitments	1,200,000,000	1,200,000,000
Commitment, capacity available to be drawn at June 30, 2017	1,000,000,000	1,000,000,000
Commitment, capacity eligible to be drawn through July 1, 2018	161,800,000	161,800,000
Reverse Mortgage | Additional Borrowing Capacity Fixed Rate Reverse Loans
Loss Contingencies [Line Items]
Commitments	300,000	300,000
Reverse Mortgage | Commitment To Fund Taxes and Insurance
Loss Contingencies [Line Items]
Commitments	28,300,000	28,300,000
Originations | Curtailment Obligation Liability
Loss Contingencies [Line Items]
Loss contingency accrual	19,800,000	19,800,000
Originations | Short Term Commitment To Lend
Loss Contingencies [Line Items]
Commitments	2,200,000,000	2,200,000,000
Originations | Commitment to Purchase Loans
Loss Contingencies [Line Items]
Commitments to purchase loans	34,400,000	34,400,000
Originations | Commitment to Purchase Loans | Representations And Warranties
Loss Contingencies [Line Items]
Loss contingency accrual	19,300,000	19,300,000
Originations | Commitment to Purchase Loans | Representations And Warranties | Maximum
Loss Contingencies [Line Items]
Commitments	67,400,000,000	67,400,000,000
Originations | Commitment To Sell Securities
Loss Contingencies [Line Items]
Commitments	3,100,000,000	3,100,000,000
Originations | Commitment to Purchase Mortgage Backed Securities
Loss Contingencies [Line Items]
Commitments to purchase loans	700,000,000	$ 700,000,000
VIE
Loss Contingencies [Line Items]
Number of securitization trusts with reimbursement obligations | Trust		11
Reimbursement obligation on LOC, if drawn	165,000,000	$ 165,000,000
Amount available on LOCs for securitization trusts	250,000,000	250,000,000
VIE Primary Beneficiary
Loss Contingencies [Line Items]
Repurchased reverse loans and real estate owned held, fair value	406,006,000	406,006,000			492,499,000
VIE Primary Beneficiary | Non-Residual Trusts
Loss Contingencies [Line Items]
Repurchased reverse loans and real estate owned held, fair value	$ 406,006,000	$ 406,006,000			$ 450,377,000
VIE Primary Beneficiary | Non-Residual Trusts | Mandatory Clean-up Call For Residential Loans
Loss Contingencies [Line Items]
Mandatory clean-up calls required when loan pool falls to percent of original pincipal balance	10.00%	10.00%
Expected period to exercise mandatory clean-up call obligation		2017 and will continue through 2019
Payment made for mandatory clean-up call obligations	$ 9,800,000
Total residential loans expected to be called	407,200,000	$ 407,200,000
Estimated call obligations in 2017	90,800,000	90,800,000
Estimated call obligations in 2018	253,300,000	253,300,000
Estimated call obligations in 2019	63,100,000	63,100,000
Estimated call obligations in third quarter of 2017	18,800,000	18,800,000
Estimated call obligations in fourth quarter of 2017	$ 72,000,000	$ 72,000,000