Receivables - Aging Analysis of Past Due Loans (Detail) (USD $) In Millions, unless otherwise specified	Mar. 31, 2013	Mar. 31, 2012	Mar. 31, 2013 First Mortgage [Member]		Dec. 31, 2012 First Mortgage [Member]		Mar. 31, 2013 Second Mortgage [Member]		Dec. 31, 2012 Second Mortgage [Member]		Mar. 31, 2013 Real estate secured [Member]		Dec. 31, 2012 Real estate secured [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, 1 - 29 Days Past Due			$ 4,264		$ 4,644		$ 573		$ 652		$ 4,837	[1]	$ 5,296	[1]
Financing Receivable, 30 - 89 days past due			2,314		2,759		254		316		2,568	[1]	3,075	[1]
Financing Receivable, 90+ days			2,649		2,748		207		239		2,856	[1]	2,987	[1]
Financing Receivable, Past Due, Total			9,227		10,151		1,034		1,207		10,261	[1]	11,358	[1]
Financing Receivable, Current			19,234		19,150		2,435		2,431		21,669	[1]	21,581	[1]
Total receivables	$ 31,930	$ 46,037	$ 28,461	[2]	$ 29,301	[2]	$ 3,469	[2]	$ 3,638	[2]	$ 31,930	[1],[2]	$ 32,939	[1],[2]

[1] Our real estate secured receivables are currently maintained on two mortgage loan servicing platforms which results in differences relating to how contractual delinquency is measured. In April 2013, we moved all closed-end real estate secured receivables onto one platform which will result in the substantial majority of our real estate secured receivables utilizing the same platform going forward.

[2] The receivable balances included in this table reflects the principal amount outstanding on the loan and certain basis adjustments to the loan such as deferred fees and costs on originated loans, purchase accounting fair value adjustments and premiums or discounts on purchased loans. However, these basis adjustments on the loans are excluded in other presentations regarding delinquent account balances.