Fair Value - Reconciliation of Beginning and Ending Balances of Company's Assets and Liabilities Measured at Fair Value on Recurring Basis Using Significant Unobservable Inputs (Level 3) (Detail) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Assets, Beginning Balance	$ 10,543,268,000	$ 6,774,912,000
Assets, Acquisition	58,680,000	242,604,000
Assets, Total Gains (Losses) Included in Comprehensive Income (Loss)	303,150,000	271,934,000
Assets, Purchases	1,438,620,000	2,707,188,000
Asset, Sales	(10,866,000)	(76,441,000)
Assets, Originations/Issuances	826,111,000	1,169,139,000
Asset, Settlements	(765,806,000)	(546,068,000)
Assets, Transfers out		0
Fair Value Assets, Ending Balance	12,393,157,000	10,543,268,000
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Liabilities, Beginning Balance	(9,341,279,000)	(6,637,938,000)
Liabilities, Acquisition	0	0
Liabilities, Total Gains (Losses) Included in Comprehensive Income (Loss)	(405,786,000)	(53,931,000)
Liabilities, Purchases	0	0
Liabilities, Sales	0	0
Liabilities, Originations/Issuances	(1,692,824,000)	(3,203,959,000)
Liabilities, Settlements	768,253,000	548,649,000
Liabilities, Transfers out		5,900,000
Fair Value Liabilities, Ending Balance	(10,671,636,000)	(9,341,279,000)
Loans Receivable Held-for-sale, Amount	1,124,615,000	1,015,607,000	45,065,000	0
Reverse Loans [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Loans Receivable Held-for-sale, Amount		0	28,500,000
Excess Servicing Spread [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Liabilities, Beginning Balance	0
Liabilities, Acquisition	0
Liabilities, Total Gains (Losses) Included in Comprehensive Income (Loss)	(2,800,000)
Liabilities, Purchases	0
Liabilities, Sales	0
Liabilities, Originations/Issuances	(75,426,000)
Liabilities, Settlements	11,915,000
Fair Value Liabilities, Ending Balance	(66,311,000)
Contingent Earn-Out Payments [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Liabilities, Beginning Balance		(6,100,000)
Liabilities, Acquisition		0
Liabilities, Total Gains (Losses) Included in Comprehensive Income (Loss)		(4,800,000)
Liabilities, Purchases		0
Liabilities, Sales		0
Liabilities, Originations/Issuances		0
Liabilities, Settlements		5,000,000
Liabilities, Transfers out		5,900,000
Fair Value Liabilities, Ending Balance		0
Mortgage-Backed Debt Related to Non-Residual Trusts [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Liabilities, Beginning Balance	(684,778,000)	(757,286,000)
Liabilities, Acquisition	0	0
Liabilities, Total Gains (Losses) Included in Comprehensive Income (Loss)	(82,253,000)	(57,678,000)
Liabilities, Purchases	0	0
Liabilities, Sales	0	0
Liabilities, Originations/Issuances	0	0
Liabilities, Settlements	113,864,000	130,186,000
Liabilities, Transfers out		0
Fair Value Liabilities, Ending Balance	(653,167,000)	(684,778,000)
HMBS Related Obligations [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Liabilities, Beginning Balance	(8,652,746,000)	(5,874,552,000)
Liabilities, Acquisition	0	0
Liabilities, Total Gains (Losses) Included in Comprehensive Income (Loss)	(324,225,000)	12,302,000
Liabilities, Purchases	0	0
Liabilities, Sales	0	0
Liabilities, Originations/Issuances	(1,617,398,000)	(3,203,959,000)
Liabilities, Settlements	642,474,000	413,463,000
Liabilities, Transfers out		0
Fair Value Liabilities, Ending Balance	(9,951,895,000)	(8,652,746,000)
Loans Receivable [Member] | Reverse Loans [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Assets, Beginning Balance	8,738,503,000	6,047,108,000
Assets, Acquisition	0	0
Assets, Total Gains (Losses) Included in Comprehensive Income (Loss)	434,197,000	112,772,000
Assets, Purchases	894,252,000	2,080,857,000
Asset, Sales	0	(76,441,000)
Assets, Originations/Issuances	611,826,000	981,390,000
Asset, Settlements	(614,413,000)	(407,183,000)
Assets, Transfers out		0
Fair Value Assets, Ending Balance	10,064,365,000	8,738,503,000
Loans Receivable [Member] | Mortgage Loans related to Non-Residual Trusts [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Assets, Beginning Balance	587,265,000	646,498,000
Assets, Acquisition	0	0
Assets, Total Gains (Losses) Included in Comprehensive Income (Loss)	111,258,000	64,848,000
Assets, Purchases	0	0
Asset, Sales	0	0
Assets, Originations/Issuances	0	0
Asset, Settlements	(112,090,000)	(124,081,000)
Assets, Transfers out		0
Fair Value Assets, Ending Balance	586,433,000	587,265,000
Loans Receivable [Member] | Charged Off Loans [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Assets, Beginning Balance	0
Assets, Acquisition	0
Assets, Total Gains (Losses) Included in Comprehensive Income (Loss)	22,501,000
Assets, Purchases	64,548,000
Asset, Sales	0
Assets, Originations/Issuances	0
Asset, Settlements	(29,832,000)
Fair Value Assets, Ending Balance	57,217,000
Receivables Related to Non-Residual Trusts [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Assets, Beginning Balance	43,545,000	53,975,000
Assets, Acquisition	0	0
Assets, Total Gains (Losses) Included in Comprehensive Income (Loss)	(8,873,000)	4,374,000
Assets, Purchases	0	0
Asset, Sales	0	0
Assets, Originations/Issuances	0	0
Asset, Settlements	(9,471,000)	(14,804,000)
Assets, Transfers out		0
Fair Value Assets, Ending Balance	25,201,000	43,545,000
Servicing Rights Carried at Fair Value [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Assets, Beginning Balance	1,131,124,000	26,382,000
Assets, Acquisition	58,680,000	242,604,000
Assets, Total Gains (Losses) Included in Comprehensive Income (Loss)	(273,502,000)	48,058,000
Assets, Purchases	479,820,000	626,331,000
Asset, Sales	(10,866,000)	0
Assets, Originations/Issuances	214,285,000	187,749,000
Asset, Settlements	0	0
Assets, Transfers out		0
Fair Value Assets, Ending Balance	1,599,541,000	1,131,124,000
Interest Rate Lock Commitments [Member] | Derivative Financial Instruments, Liabilities [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Liabilities, Beginning Balance	(3,755,000)	0
Liabilities, Acquisition	0	0
Liabilities, Total Gains (Losses) Included in Comprehensive Income (Loss)	3,492,000	(3,755,000)
Liabilities, Purchases	0	0
Liabilities, Sales	0	0
Liabilities, Originations/Issuances	0	0
Liabilities, Settlements	0	0
Liabilities, Transfers out		0
Fair Value Liabilities, Ending Balance	(263,000)	(3,755,000)
Interest Rate Lock Commitments [Member] | Freestanding derivative instruments (IRLCs) [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Assets, Beginning Balance	42,831,000	949,000
Assets, Acquisition	0	0
Assets, Total Gains (Losses) Included in Comprehensive Income (Loss)	17,569,000	41,882,000
Assets, Purchases	0	0
Asset, Sales	0	0
Assets, Originations/Issuances	0	0
Asset, Settlements	0	0
Assets, Transfers out		0
Fair Value Assets, Ending Balance	$ 60,400,000	$ 42,831,000