Medium- And Long-Term Debt (Schedule Of Medium- And Long-Term Debt) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011
Debt Instruments [Line Items]
Total medium- and long-term debt	$ 4,720	$ 4,944
Parent Company
Debt Instruments [Line Items]
Subordinated notes	330	368
Total medium- and long-term debt	629	666
Subsidiaries
Debt Instruments [Line Items]
Subordinated notes	2,058	2,081
Total medium- and long-term debt	4,091	4,278
4.80% subordinated notes due 2015 [Member] | Parent Company
Debt Instruments [Line Items]
Subordinated notes	330	338
Fixed Interest Rate	4.80%	4.80%
Maturity Date	Dec. 31, 2015	Dec. 31, 2015
Floating-rate subordinated notes related to trust preferred securities due 2012 [Member] | Parent Company
Debt Instruments [Line Items]
Subordinated notes	0	30
Maturity Date	Dec. 31, 2012	Dec. 31, 2012
3.00% notes due 2015 [Member] | Parent Company
Debt Instruments [Line Items]
Medium-term notes	299	298
Fixed Interest Rate	3.00%	3.00%
Maturity Date	Dec. 31, 2015	Dec. 31, 2015
7.375% subordinated notes due 2013 [Member] | Subsidiaries
Debt Instruments [Line Items]
Subordinated notes	51	53
Fixed Interest Rate	7.375%	7.375%
Maturity Date	Dec. 31, 2013	Dec. 31, 2013
5.70% subordinated notes due 2014 [Member] | Subsidiaries
Debt Instruments [Line Items]
Subordinated notes	267	276
Fixed Interest Rate	5.70%	5.70%
Maturity Date	Dec. 31, 2014	Dec. 31, 2014
5.75% subordinated notes due 2016 [Member] | Subsidiaries
Debt Instruments [Line Items]
Subordinated notes	694	699
Fixed Interest Rate	5.75%	5.75%
Maturity Date	Dec. 31, 2016	Dec. 31, 2016
5.20% subordinated notes due 2017 [Member] | Subsidiaries
Debt Instruments [Line Items]
Subordinated notes	593	595
Fixed Interest Rate	5.20%	5.20%
Maturity Date	Dec. 31, 2017	Dec. 31, 2017
Floating-rate based on LIBOR index subordinated notes due 2018 [Member] | Subsidiaries
Debt Instruments [Line Items]
Subordinated notes	26	26
Maturity Date	Dec. 31, 2018	Dec. 31, 2018
8.375% subordinated notes due 2024 [Member] | Subsidiaries
Debt Instruments [Line Items]
Subordinated notes	186	189
Fixed Interest Rate	8.375%	8.375%
Maturity Date	Dec. 31, 2024	Dec. 31, 2024
7.875% subordinated notes due 2026 [Member] | Subsidiaries
Debt Instruments [Line Items]
Subordinated notes	241	243
Fixed Interest Rate	7.875%	7.875%
Maturity Date	Dec. 31, 2026	Dec. 31, 2026
Floating-rate based on LIBOR indices due 2012 [Member] | Subsidiaries
Debt Instruments [Line Items]
Medium-term notes	0	158
Maturity Date	Dec. 31, 2012	Dec. 31, 2012
Floating-rate based on LIBOR indices due 2013 to 2014 [Member] | Subsidiaries
Debt Instruments [Line Items]
Federal Home Loan Bank advances	2,000	2,000
Maturity date range, start	Dec. 31, 2013	Dec. 31, 2013
Maturity date range, end	Dec. 31, 2014	Dec. 31, 2014
6.0% - 6.4% fixed-rate notes due 2020 [Member] | Subsidiaries
Debt Instruments [Line Items]
Other Notes	$ 33	$ 39
Interest rate minimum	6.00%	6.00%
Interest rate maximum	6.40%	6.40%
Maturity Date	Dec. 31, 2020	Dec. 31, 2020