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	Dec. 31, 2014	Dec. 31, 2013
HTM securities	$ 20,240	$ 18,101
Deposits	129,040	127,475
Long-term debt	23,312	21,493
Carrying Amount [Member]
HTM securities	20,240	18,101
Loans and leases,net of ALLL (excluding covered)	117,259	112,264
Acquired from FDIC loans, net of ALLL	1,151	1,921
FDIC loss share receivable	534	843
Deposits	129,040	127,475
FDIC loss share payable	697	669
Long-term debt	23,312	21,493
Estimate of Fair Value, Fair Value Disclosure [Member]
HTM securities	20,313	17,530
Loans and leases,net of ALLL (excluding covered)	117,268	112,261
Acquired from FDIC loans, net of ALLL	1,337	2,200
FDIC loss share receivable	123	464
Deposits	129,259	127,810
FDIC loss share payable	696	652
Long-term debt	24,063	22,313
Level 2 [Member] | Estimate of Fair Value, Fair Value Disclosure [Member]
HTM securities	20,313	17,491
Loans and leases,net of ALLL (excluding covered)	0	0
Acquired from FDIC loans, net of ALLL	0	0
FDIC loss share receivable	0	0
Deposits	129,259	127,810
FDIC loss share payable	0	0
Long-term debt	24,063	22,313
Level 3 [Member] | Estimate of Fair Value, Fair Value Disclosure [Member]
HTM securities	0	39
Loans and leases,net of ALLL (excluding covered)	117,268	112,261
Acquired from FDIC loans, net of ALLL	1,337	2,200
FDIC loss share receivable	123	464
Deposits	0	0
FDIC loss share payable	696	652
Long-term debt	$ 0	$ 0