Fair Value Disclosures (Carrying Amounts and Fair Values of Financial Assets and Liabilities Not Recorded at Fair Value) (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
HTM securities	$ 13,119	$ 13,594
FDIC loss share receivable	368	479
Deposits	131,352	133,075
Long-term debt	18,316	19,114
Carrying Amount [Member]
HTM securities	13,119	13,594
Loans and leases,net of ALLL (excluding covered)	109,355	109,419
Covered loans, net of ALLL	2,866	3,166
FDIC loss share receivable	368	479
Deposits	131,352	133,075
Long-term debt	18,316	19,114
Estimate of Fair Value, Fair Value Disclosure [Member]
HTM securities	13,295	13,848
Loans and leases,net of ALLL (excluding covered)	109,755	109,621
Covered loans, net of ALLL	3,315	3,661
FDIC loss share receivable	68	149
Deposits	131,611	133,377
Long-term debt	19,772	20,676
Level 2 [Member] | Estimate of Fair Value, Fair Value Disclosure [Member]
HTM securities	13,258	13,810
Loans and leases,net of ALLL (excluding covered)	0	0
Covered loans, net of ALLL	0	0
FDIC loss share receivable	0	0
Deposits	131,611	133,377
Long-term debt	19,772	20,676
Level 3 [Member] | Estimate of Fair Value, Fair Value Disclosure [Member]
HTM securities	37	38
Loans and leases,net of ALLL (excluding covered)	109,755	109,621
Covered loans, net of ALLL	3,315	3,661
FDIC loss share receivable	68	149
Deposits	0	0
Long-term debt	$ 0	$ 0