Commitments and Contingencies - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Nov. 01, 2012	Jul. 01, 2014
Loss Contingencies [Line Items]
Mandatory repurchase obligation	$ 11,000,000
Lease Expiration Date	Dec. 31, 2023
Operating Leases, Rent Expense	26,700,000	22,100,000	12,300,000
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]
Mandatory repurchase obligation	87,000,000
Range of reasonably possible losses, minimum	900,000
Range of reasonably possible losses, maximum	2,300,000
Representations And Warranties [Member] | Commitment to Repurchase Loans [Member]
Loss Contingencies [Line Items]
Commitments to sell loans	31,200,000,000
Curtailment Obligation Liability [Member]
Loss Contingencies [Line Items]
Mandatory repurchase obligation	60,800,000			46,000,000
Loss contingency recorded in current period	500,000
Loss contingency associated with prior servicer	5,600,000
Additional amount of potential loss exposure from similar claims	157,000,000
Reverse Mortgage [Member] | Additional Borrowing Capacity Floating Rate Reverse Mortgage Loans [Member]
Loss Contingencies [Line Items]
Commitments to sell loans	1,100,000,000
Reverse Mortgage [Member] | Additional Borrowing Capacity Fixed Rate Reverse Mortgage Loans [Member]
Loss Contingencies [Line Items]
Commitments to sell loans	1,700,000
Reverse Mortgage [Member] | Commitment to Lend [Member]
Loss Contingencies [Line Items]
Commitments to sell loans	142,500,000
Reverse Mortgage [Member] | Loan Purchase Commitments [Member]
Loss Contingencies [Line Items]
Commitments to purchase loans	6,700,000
Reverse Mortgage [Member] | Loan Sale Commitments [Member]
Loss Contingencies [Line Items]
Commitments to sell loans	135,900,000
Originations [Member] | Commitment to Lend [Member]
Loss Contingencies [Line Items]
Commitments to sell loans	2,800,000,000
Originations [Member] | Commitment to Purchase Loans [Member]
Loss Contingencies [Line Items]
Commitments to purchase loans	19,500,000
Originations [Member] | Commitment To Sell Securities [Member]
Loss Contingencies [Line Items]
Commitments to sell loans	5,000,000,000
Originations [Member] | Commitment to Purchase Mortgage Backed Securities [Member]
Loss Contingencies [Line Items]
Commitments to sell loans	1,800,000,000
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	165,000,000.0
Amount Of Loc Available For Eleven Securitization Trusts	265,200,000	273,600,000
VIE Primary Beneficiary [Member] | Non Residual Trusts [Member]
Loss Contingencies [Line Items]
Expected Period To Exercise Mandatory Clean Up Call Obligation	2017 and continuing through 2019
Outstanding Balance Of Collateral For Mandatory Clean Up Call Obligation	417,200,000
Variable Interest Entity, Not Primary Beneficiary [Member] | WCO [Member]
Loss Contingencies [Line Items]
Capital Commitment					20,000,000
Capital Commitment, Amount Remaining	12,900,000
Servicing Arrangements Associated With Transfers Of Forward Loans [Member]
Loss Contingencies [Line Items]
Unpaid Principal Balance of Sold Loans	$ 28,457,216,000	$ 14,672,986,000