Commitments, Contingencies and Guarantees - Additional Information 1 (Detail) (USD $)	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2013 Subsidiary	Jun. 30, 2012	Jun. 30, 2013 Subsidiary	Jun. 30, 2012	Dec. 31, 2012	Mar. 31, 2013	Mar. 31, 2012	Dec. 31, 2011
Commitments, Contingencies And Guarantees [Line Items]
Original principal balance of mortgage loans originated and sold by subsidiaries between 2005 and 2008 into Uninsured Securitizations	$ 48,000,000,000		$ 48,000,000,000
Original principal balance of mortgage loans originated and sold by subsidiaries between 2005 and 2008 to private investors	22,000,000,000		22,000,000,000
Original principal balance of mortgage loans originated and sold by subsidiaries between 2005 and 2008 to various known and unknown investors			10,000,000,000
Original principal balance of mortgage loans originated and sold to non-affiliates by subsidiaries between 2005 and 2008	111,000,000,000		111,000,000,000
Unpaid principal balance	29,000,000,000		29,000,000,000		32,000,000,000
Active loan losses	20,000,000,000		20,000,000,000
Minimum number of days past due for delinquent loan status	90 Days		90 Days
Original principal balance of mortgage loans lacking information about the current holders or underlying credit performance			7,000,000,000
Open repurchase requests	2,565,000,000		2,565,000,000		2,419,000,000			2,091,000,000
Majority of new repurchase demands received from mortgage loans			1,200,000,000
Loans sold	111,000,000,000
Original principal balance of mortgage loans originated and sold by subsidiaries between 2005 and 2008 into Active Insured Securitizations	16,000,000,000		16,000,000,000
Reserve liability	1,156,000,000	1,002,000,000	1,156,000,000	1,002,000,000	899,000,000	994,000,000	1,101,000,000	943,000,000
Number of subsidiaries acquired that originated residential mortgage loans	3		3
Provision for repurchase losses	183,000,000	180,000,000	280,000,000	349,000,000	349,000,000
Net realized losses	21,000,000	279,000,000	23,000,000	290,000,000	393,000,000
High end of range of estimated reasonably possible future losses from representation and warranty claims	2,500,000,000		2,500,000,000		2,700,000,000
Uninsured Securitizations and Other [Member]
Commitments, Contingencies And Guarantees [Line Items]
Original principal balance of mortgage loans originated and sold by subsidiaries between 2005 and 2008 into unknown current ownership	80,000,000,000		80,000,000,000
Original principal balance of mortgage loans originated and sold to non-affiliates by subsidiaries between 2005 and 2008	80,000,000,000		80,000,000,000
Unpaid principal balance	21,000,000,000		21,000,000,000		23,000,000,000
Open repurchase requests	903,000,000		903,000,000		781,000,000			672,000,000
GSEs and Active Insured Securitizations [Member]
Commitments, Contingencies And Guarantees [Line Items]
Original principal balance of mortgage loans originated and sold to non-affiliates by subsidiaries between 2005 and 2008	27,000,000,000		27,000,000,000
Loans sold	27,000,000,000
Reserve liability	1,003,000,000		1,003,000,000		817,000,000
GSE's [Member]
Commitments, Contingencies And Guarantees [Line Items]
Original principal balance of mortgage loans originated and sold to non-affiliates by subsidiaries between 2005 and 2008	11,000,000,000		11,000,000,000
Unpaid principal balance	3,000,000,000		3,000,000,000		4,000,000,000
Open repurchase requests	53,000,000		53,000,000		59,000,000			176,000,000
Loans sold			27,000,000,000
Inactive Insured Securitizations [Member]
Commitments, Contingencies And Guarantees [Line Items]
Original principal balance of mortgage loans originated and sold to non-affiliates by subsidiaries between 2005 and 2008	4,000,000,000		4,000,000,000
Private Investors [Member]
Commitments, Contingencies And Guarantees [Line Items]
Original principal balance of mortgage loans originated and sold by subsidiaries between 2005 and 2008 to private investors	$ 22,000,000,000		$ 22,000,000,000