Commitments and Contingencies - Additional Information (Detail) (USD $)	3 Months Ended
	Mar. 31, 2015	Dec. 31, 2014	Jul. 01, 2014	Nov. 01, 2012
Loss Contingencies [Line Items]
Capital Commitment			$ 20,000,000
Capital Commitment, Amount Remaining	9,300,000
Loss contingency recorded in current period	94,000,000
Civil penalty settlement		15,000,000
Tax separation agreement date	Apr. 17, 2009
Income tax examination, period of letters issued to prior parent for proposed changes in specified tax years	30 days
Pending Litigation [Member]
Loss Contingencies [Line Items]
Range of reasonably possible losses, minimum	0
Range of reasonably possible losses, maximum	2,500,000
Representations And Warranties [Member]
Loss Contingencies [Line Items]
Mandatory repurchase obligation	12,100,000
Representations And Warranties [Member] | Commitment to Purchase Loans [Member]
Loss Contingencies [Line Items]
Commitments to sell loans	35,700,000,000
Curtailment Obligation Liability [Member]
Loss Contingencies [Line Items]
Mandatory repurchase obligation	86,400,000			46,000,000
Loss contingency recorded in current period	16,500,000
Additional amount of potential loss exposure from similar claims	128,400,000
ConvenienceFees [Member]
Loss Contingencies [Line Items]
Loss Contingency, Accrual, Current		18,000,000
Delays in Service [Member]
Loss Contingencies [Line Items]
Loss Contingency, Accrual, Current		30,000,000
Reverse Mortgage [Member] | Additional Borrowing Capacity Floating Rate Reverse Mortgage Loans [Member]
Loss Contingencies [Line Items]
Commitments to sell loans	1,200,000,000
Reverse Mortgage [Member] | Additional Borrowing Capacity Fixed Rate Reverse Mortgage Loans [Member]
Loss Contingencies [Line Items]
Commitments to sell loans	1,400,000
Reverse Mortgage [Member] | Commitment to Lend [Member]
Loss Contingencies [Line Items]
Commitments to sell loans	200,000,000
Reverse Mortgage [Member] | Loan Purchase Commitments [Member]
Loss Contingencies [Line Items]
Commitments to purchase loans	6,400,000
Reverse Mortgage [Member] | Loan Sale Commitments [Member]
Loss Contingencies [Line Items]
Commitments to sell loans	164,900,000
Originations [Member] | Commitment to Lend [Member]
Loss Contingencies [Line Items]
Commitments to sell loans	4,600,000,000
Originations [Member] | Commitment to Purchase Loans [Member]
Loss Contingencies [Line Items]
Commitments to purchase loans	56,100,000
Originations [Member] | Commitment To Sell Securities [Member]
Loss Contingencies [Line Items]
Commitments to sell loans	7,100,000,000
Originations [Member] | Commitment to Purchase Mortgage Backed Securities [Member]
Loss Contingencies [Line Items]
Commitments to sell loans	2,700,000,000
VIE [Member]
Loss Contingencies [Line Items]
Aggregate number of securitization trusts consolidated and not consolidated with reimbursement obligations	11
Reimbursement obligation of LOC, if drawn	165,000,000
Amount of LOCs available for eleven securitization trusts	263,500,000
VIE Primary Beneficiary [Member] | Non-Residual Trusts [Member]
Loss Contingencies [Line Items]
Mandatory Cleanup Calls Must Be Performed On Non Residual Trusts When Each Loan Pool Falls To Percent Of Original Principal Balance	10.00%
Expected period to exercise mandatory clean-up call obligation	2017 and continuing through 2019
Outstanding balance of collateral for mandatory clean-up call obligation	$ 417,300,000