Fair Value - Carrying Values and Estimated Fair Values of Financial Assets and Liabilities Required to be Disclosed at Fair Value (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012	Sep. 30, 2012	Dec. 31, 2011
Financial assets
Cash and cash equivalents	$ 405,355	$ 442,054	$ 38,926	$ 18,739
Restricted cash and cash equivalents	922,522	653,338
Residential loans carried at amortized cost	1,417,020	1,490,321
Insurance premium receivables	106,176	107,824
Servicer and protective advances, net	1,186,066	173,047
Financial liabilities
Payables to insurance carriers	81,415	51,377
Servicer payables	851,231	587,929
Servicing advance liabilities	834,160	100,164
Debt	3,269,710	1,146,249
Mortgage-backed debt carried at amortized cost	1,939,082	2,072,728
Carrying Amount [Member] | Level 1 [Member]
Financial assets
Cash and cash equivalents	405,355	442,054
Restricted cash and cash equivalents	922,522	653,338
Other	101,934	97,210
Financial liabilities
Other	368,485	183,885
Servicer payables	851,231	587,929
Carrying Amount [Member] | Level 3 [Member]
Financial assets
Residential loans carried at amortized cost	1,417,020	1,490,321
Insurance premium receivables	106,176	107,824
Servicer and protective advances, net	1,186,066	173,047
Financial liabilities
Payables to insurance carriers	81,415	51,377
Servicing advance liabilities	833,695	99,508
Mortgage-backed debt carried at amortized cost	1,216,302	1,298,999
Carrying Amount [Member] | Level 2 [Member]
Financial liabilities
Debt	3,235,774	1,115,804
Estimated Fair Value [Member] | Level 1 [Member]
Financial assets
Cash and cash equivalents	405,355	442,054
Restricted cash and cash equivalents	922,522	653,338
Other	101,934	97,210
Financial liabilities
Other	368,485	183,885
Servicer payables	851,231	587,929
Estimated Fair Value [Member] | Level 3 [Member]
Financial assets
Residential loans carried at amortized cost	1,367,031	1,436,592
Insurance premium receivables	100,045	101,238
Servicer and protective advances, net	1,111,042	160,632
Financial liabilities
Payables to insurance carriers	80,310	50,614
Servicing advance liabilities	834,160	99,915
Mortgage-backed debt carried at amortized cost	1,220,142	1,300,979
Estimated Fair Value [Member] | Level 2 [Member]
Financial liabilities
Debt	$ 3,310,927	$ 1,165,811