Fair Value - Schedule of Assets and Liabilities Measured at Fair Value on Recurring Basis Utilizing Significant Unobservable Inputs Reconciliation (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value, Beginning Balance	$ 13,089,216	$ 12,393,157
Total Gains (Losses) Included in Comprehensive Loss	(70,232)	(125,511)
Purchases and Other	445,269	1,000,477
Sales	(247,829)	(76,686)
Originations/ Issuances	644,975	1,015,689
Settlements	(1,403,657)	(1,117,910)
Transfers out of Level 3	(212,630)
Fair Value, Ending Balance	12,245,112	13,089,216	$ 12,393,157
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value, Beginning Balance	(11,347,792)	(10,671,636)
Total Gains (Losses) Included in Comprehensive Loss	(315,698)	(146,017)
Purchases and Other	0	0
Sales	108,887	0
Originations/ Issuances	(988,042)	(1,687,074)
Settlements	1,514,978	1,156,935
Transfers out of Level 3	0
Fair Value, Ending Balance	(11,027,667)	(11,347,792)	(10,671,636)
Mortgage servicing rights sold	458,541	60,094	10,866
Net gains (losses) on sales of loans	409,448	453,840	462,172
Freestanding Derivative Instruments [Member] | Interest Rate Lock Commitments [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value, Beginning Balance	(1,070)	(263)
Total Gains (Losses) Included in Comprehensive Loss	(3,123)	(807)
Purchases and Other	0	0
Sales	0	0
Originations/ Issuances	0	0
Settlements	0	0
Transfers out of Level 3	0
Fair Value, Ending Balance	(4,193)	(1,070)	(263)
Servicing Rights Related Liabilities [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value, Beginning Balance	(117,000)	(66,311)
Total Gains (Losses) Included in Comprehensive Loss	(3,921)	(7,741)
Purchases and Other	0	0
Sales	108,887	0
Originations/ Issuances	(27,886)	(64,593)
Settlements	39,920	21,645
Transfers out of Level 3	0
Fair Value, Ending Balance	0	(117,000)	(66,311)
Losses on liabilities from instrument-specific credit risk	15,800
Mortgage-Backed Debt Related to Non-Residual Trusts [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value, Beginning Balance	(582,340)	(653,167)
Total Gains (Losses) Included in Comprehensive Loss	(29,355)	(33,142)
Purchases and Other	0	0
Sales	0	0
Originations/ Issuances	0	0
Settlements	97,670	103,969
Transfers out of Level 3	0
Fair Value, Ending Balance	(514,025)	(582,340)	(653,167)
HMBS Related Obligations [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value, Beginning Balance	(10,647,382)	(9,951,895)
Total Gains (Losses) Included in Comprehensive Loss	(279,299)	(104,327)
Purchases and Other	0	0
Sales	0	0
Originations/ Issuances	(960,156)	(1,622,481)
Settlements	1,377,388	1,031,321
Transfers out of Level 3	0
Fair Value, Ending Balance	(10,509,449)	(10,647,382)	(9,951,895)
Reverse Loans [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value, Beginning Balance	10,763,816	10,064,365
Total Gains (Losses) Included in Comprehensive Loss	338,321	202,494
Purchases and Other	437,540	762,657
Sales	0	(16,592)
Originations/ Issuances	459,280	708,948
Settlements	(1,256,035)	(958,056)
Transfers out of Level 3	0
Fair Value, Ending Balance	10,742,922	10,763,816	10,064,365
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Reverse loans sold		16,600
Net gains (losses) on sales of loans		100
Mortgage Loans Related To Non Residual Trusts [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value, Beginning Balance	526,016	586,433
Total Gains (Losses) Included in Comprehensive Loss	19,464	41,643
Purchases and Other	0	0
Sales	0	0
Originations/ Issuances	0	0
Settlements	(95,103)	(102,060)
Transfers out of Level 3	0
Fair Value, Ending Balance	450,377	526,016	586,433
Charged-off Loans [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value, Beginning Balance	49,307	57,217
Total Gains (Losses) Included in Comprehensive Loss	41,391	41,803
Purchases and Other	0	0
Sales	0	0
Originations/ Issuances	0	0
Settlements	(43,735)	(49,713)
Transfers out of Level 3	0
Fair Value, Ending Balance	46,963	49,307	57,217
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Gains on assets from instrument-specific credit risk	20,700	18,500
Receivables Related to Non-Residual Trusts [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value, Beginning Balance	16,542	25,201
Total Gains (Losses) Included in Comprehensive Loss	6,601	(1,178)
Purchases and Other	0	0
Sales	0	0
Originations/ Issuances	0	0
Settlements	(8,110)	(7,481)
Transfers out of Level 3	0
Fair Value, Ending Balance	15,033	16,542	25,201
Servicing Rights Carried at Fair Value [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value, Beginning Balance	1,682,016	1,599,541
Total Gains (Losses) Included in Comprehensive Loss	(478,558)	(401,992)
Purchases and Other	7,729	237,820
Sales	(247,829)	(60,094)
Originations/ Issuances	185,695	306,741
Settlements	0	0
Transfers out of Level 3	(212,630)
Fair Value, Ending Balance	936,423	1,682,016	1,599,541
Freestanding Derivative Instruments [Member] | Interest Rate Lock Commitments [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value, Beginning Balance	51,519	60,400
Total Gains (Losses) Included in Comprehensive Loss	2,549	(8,281)
Purchases and Other	0	0
Sales	0	0
Originations/ Issuances	0	0
Settlements	(674)	(600)
Transfers out of Level 3	0
Fair Value, Ending Balance	$ 53,394	$ 51,519	$ 60,400