Variable Interest Entities - Summary of Carrying Amounts of Assets and Liabilities (Detail) (USD $)	Jun. 30, 2013	Dec. 31, 2012	Jun. 30, 2012
Assets
Restricted cash and cash equivalents	$ 1,057,503,000	$ 653,338,000
Residential loans at amortized cost, net	1,443,707,000	1,490,321,000
Residential loans at fair value	10,184,477,000	6,710,211,000
Receivables, at fair value	269,021,000	259,009,000
Servicer and protective advances, net	1,044,410,000	173,047,000
Other assets	375,806,000	144,830,000
Total assets	16,930,212,000	10,978,177,000	4,086,317,000
Liabilities
Payables and accrued liabilities	701,349,000	260,610,000
Servicing advance liabilities	737,629,000	100,164,000
Mortgage-backed debt	1,980,868,000	2,072,728,000
Total liabilities	15,856,185,000	10,083,249,000
VIE Primary Beneficiary [Member]
Assets
Restricted cash and cash equivalents	57,278,000	58,253,000
Residential loans at amortized cost, net	1,427,715,000	1,475,782,000
Residential loans at fair value	613,627,000	646,498,000
Receivables, at fair value	50,890,000	53,975,000
Servicer and protective advances, net	78,309,000	77,082,000
Other assets	58,274,000	62,683,000
Total assets	2,286,093,000	2,374,273,000
Liabilities
Payables and accrued liabilities	8,753,000	9,007,000
Servicing advance liabilities	65,505,000	64,552,000
Mortgage-backed debt	1,980,868,000	2,072,728,000
Total liabilities	2,055,126,000	2,146,287,000
Residual Trusts [Member] | VIE Primary Beneficiary [Member]
Assets
Restricted cash and cash equivalents	43,153,000	43,856,000
Residential loans at amortized cost, net	1,427,715,000	1,475,782,000
Residential loans at fair value
Receivables, at fair value
Servicer and protective advances, net
Other assets	56,559,000	60,669,000
Total assets	1,527,427,000	1,580,307,000
Liabilities
Payables and accrued liabilities	8,753,000	9,007,000
Servicing advance liabilities
Mortgage-backed debt	1,259,788,000	1,315,442,000
Total liabilities	1,268,541,000	1,324,449,000
Non-Residual Trusts [Member] | VIE Primary Beneficiary [Member]
Assets
Restricted cash and cash equivalents	14,125,000	14,397,000
Residential loans at amortized cost, net
Residential loans at fair value	613,627,000	646,498,000
Receivables, at fair value	50,890,000	53,975,000
Servicer and protective advances, net
Other assets	1,715,000	2,014,000
Total assets	680,357,000	716,884,000
Liabilities
Payables and accrued liabilities
Servicing advance liabilities
Mortgage-backed debt	721,080,000	757,286,000
Total liabilities	721,080,000	757,286,000
Servicer and Protective Advance Financing [Member] | VIE Primary Beneficiary [Member]
Assets
Restricted cash and cash equivalents
Residential loans at amortized cost, net
Residential loans at fair value
Receivables, at fair value
Servicer and protective advances, net	78,309,000	77,082,000
Other assets
Total assets	78,309,000	77,082,000
Liabilities
Payables and accrued liabilities
Servicing advance liabilities	65,505,000	64,552,000
Mortgage-backed debt
Total liabilities	$ 65,505,000	$ 64,552,000