Fair Value Of Financial Instruments (Difference Between Aggregate Fair Value And Aggregate Remaining Contractual Principal Balance Outstanding) (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Schedule of Fair Value of Separate Accounts by Major Category of Investment [Line Items]
Loans receivable, Contractual Outstanding Principal	$ 2,770	$ 3,481
Variable interest entity notes, Contractual Outstanding Principal	9,021	13,583
Loans receivable, Fair Value	1,881	2,046
Variable interest entity notes, Fair Value	3,659	4,754
Loans receivable, Difference	889	1,435
Variable interest entity notes, Difference	5,362	8,829
Residential Mortgage Loans [Member]
Schedule of Fair Value of Separate Accounts by Major Category of Investment [Line Items]
Loans receivable, Contractual Outstanding Principal	2,307	2,769
Loans receivable, 90 days or more past due, Contractual Outstanding Principal	244	259
Loans receivable, Fair Value	1,735	1,895
Loans receivable, 90 days or more past due, Fair Value	54
Loans receivable, Difference	572	874
Loans receivable, 90 days or more past due, Difference	190	259
Other Loans [Member]
Schedule of Fair Value of Separate Accounts by Major Category of Investment [Line Items]
Loans receivable, Contractual Outstanding Principal	22	129
Loans receivable, 90 days or more past due, Contractual Outstanding Principal	197	324
Loans receivable, Fair Value	22	43
Loans receivable, 90 days or more past due, Fair Value	70	108
Loans receivable, Difference		86
Loans receivable, 90 days or more past due, Difference	$ 127	$ 216