Fair Value Of Financial Instruments (Aggregate Fair Value And Remaining Contractual Principal Balance Outstanding On Fair Value Option) (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Non Variable Interest Entity [Member]
Schedule Of Fair Value Of Separate Accounts By Major Category Of Investment [Line Items]
Medium-term notes, contractual outstanding principal	$ 242	$ 276
Medium-term notes, fair value	197	203
Medium-term notes, difference	45	73
Variable Interest Entity [Member]
Schedule Of Fair Value Of Separate Accounts By Major Category Of Investment [Line Items]
Loans receivable, contractual outstanding principal	2,502	2,077
Variable interest entity notes, contractual outstanding principal	3,584	3,787
Loans receivable, fair value	2,142	1,612
Variable interest entity notes, fair value	2,479	2,356
Loans receivable, difference	360	465
Variable interest entity notes, difference	1,105	1,431
Residential Mortgage Loans [Member] | Variable Interest Entity [Member]
Schedule Of Fair Value Of Separate Accounts By Major Category Of Investment [Line Items]
Loans receivable, contractual outstanding principal	1,554	1,846
Loans receivable, 90 days or more past due, contractual outstanding principal	227	231
Loans receivable, fair value	1,377	1,562
Loans receivable, 90 days or more past due, fair value	54	50
Loans receivable, difference	177	284
Loans receivable, 90 days or more past due, difference	173	181
Other Loans [Member] | Variable Interest Entity [Member]
Schedule Of Fair Value Of Separate Accounts By Major Category Of Investment [Line Items]
Loans receivable, contractual outstanding principal	721
Loans receivable, fair value	711
Loans receivable, difference	$ 10