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	Mar. 31, 2015	Dec. 31, 2014
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	$ 215	$ 242
Medium-term notes, fair value	180	197
Medium-term notes, difference	35	45
Variable Interest Entity [Member]
Schedule Of Fair Value Of Separate Accounts By Major Category Of Investment [Line Items]
Loans receivable, contractual outstanding principal	1,876	2,502
Variable interest entity notes, contractual outstanding principal	4,000	3,584
Loans receivable, fair value	1,480	2,142
Variable interest entity notes, fair value	2,653	2,479
Loans receivable, difference	396	360
Variable interest entity notes, difference	1,347	1,105
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	1,478	1,554
Loans receivable, 90 days or more past due, contractual outstanding principal	220	227
Loans receivable, fair value	1,320	1,377
Loans receivable, 90 days or more past due, fair value	52	54
Loans receivable, difference	158	177
Loans receivable, 90 days or more past due, difference	168	173
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	108	721
Loans receivable, 90 days or more past due, contractual outstanding principal	70
Loans receivable, fair value	108	711
Loans receivable, difference	0	10
Loans receivable, 90 days or more past due, difference	$ 70