Asset Quality (Details 1) (USD $) In Millions, unless otherwise specified	Mar. 31, 2012	Dec. 31, 2011	Mar. 31, 2011
Financing Receivable, Impaired [Line Items]
Recorded Investment	$ 359	$ 388	$ 493
Unpaid Principal Balance	780	751	1,127
Specific Allowance	38	51	39
Average Recorded Investment	374	505	557
Impaired Financing Receivable with No Related Allowance [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment		218	361
Unpaid Principal Balance		548	884
Average Recorded Investment		304	375
Commercial, financial and agricultural [Member] | Impaired Financing Receivable with No Related Allowance [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	77	88	84
Unpaid Principal Balance	189	195	178
Average Recorded Investment	83	75	72
Commercial, financial and agricultural [Member] | Impaired Financing Receivable with Related Allowance [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	49	62	63
Unpaid Principal Balance	60	70	117
Specific Allowance	19	26	25
Average Recorded Investment	55	75	76
Commercial real estate: Commercial Mortgage [Member] | Impaired Financing Receivable with No Related Allowance [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	113	100	156
Unpaid Principal Balance	252	240	298
Average Recorded Investment	106	131	159
Commercial real estate: Commercial Mortgage [Member] | Impaired Financing Receivable with Related Allowance [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	69	96	62
Unpaid Principal Balance	111	115	115
Specific Allowance	16	21	13
Average Recorded Investment	83	91	74
Commercial real estate: Construction [Member] | Impaired Financing Receivable with No Related Allowance [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	47	30	121
Unpaid Principal Balance	164	113	408
Average Recorded Investment	39	98	144
Commercial real estate: Construction [Member] | Impaired Financing Receivable with Related Allowance [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	4	12	7
Unpaid Principal Balance	4	18	11
Specific Allowance	3	4	1
Average Recorded Investment	8	29	26
Commercial Real Estate Loans [Member] | Impaired Financing Receivable with No Related Allowance [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	160	130	277
Unpaid Principal Balance	416	353	706
Average Recorded Investment	145	229	303
Commercial Real Estate Loans [Member] | Impaired Financing Receivable with Related Allowance [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	73	108	69
Unpaid Principal Balance	115	133	126
Specific Allowance	19	25	14
Average Recorded Investment	91	120	100
Commercial Lease Financing [Member] | Impaired Financing Receivable with Related Allowance [Member]
Financing Receivable, Impaired [Line Items]
Average Recorded Investment		6	6
Commercial Loans [Member] | Impaired Financing Receivable with No Related Allowance [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	237
Unpaid Principal Balance	605
Average Recorded Investment	228
Commercial Loans [Member] | Impaired Financing Receivable with Related Allowance [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	122	170	132
Unpaid Principal Balance	175	203	243
Specific Allowance	38	51	39
Average Recorded Investment	$ 146	$ 201	$ 182