Loans and Leases and the Allowance for Credit Losses - Summary of Current, Past Due and Nonaccrual Loans (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current	$ 63,525,686	$ 61,664,881
30-89 Days past due	517,090	704,658
Purchased impaired	236,662	330,792
Nonaccrual	847,784	874,156
Loans and leases, net of unearned discount	65,572,359	64,073,159
Commercial, Financial, Leasing, etc. [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current	18,855,986	18,489,474
30-89 Days past due	41,296	77,538
Purchased impaired	14,777	15,706
Nonaccrual	191,250	110,739
Loans and leases, net of unearned discount	19,112,009	18,705,216
Commercial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current	21,646,276	21,236,071
30-89 Days past due	101,671	145,749
Purchased impaired	62,739	88,034
Nonaccrual	173,285	173,048
Loans and leases, net of unearned discount	22,044,855	21,741,858
Residential Builder and Developer [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current	1,211,005	1,025,984
30-89 Days past due	21,432	8,486
Purchased impaired	96,917	137,544
Nonaccrual	73,296	96,427
Loans and leases, net of unearned discount	1,418,051	1,276,512
Other commercial construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current	3,392,260	2,986,598
30-89 Days past due	18,749	42,234
Purchased impaired	36,114	57,707
Nonaccrual	27,375	35,268
Loans and leases, net of unearned discount	3,479,941	3,129,838
Residential [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current	7,578,177	7,630,368
30-89 Days past due	222,214	295,131
Purchased impaired	23,551	29,184
Nonaccrual	183,681	252,805
Loans and leases, net of unearned discount	8,313,438	8,545,837
Residential Alt-A [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current	254,188	283,253
30-89 Days past due	15,765	18,009
Purchased impaired
Nonaccrual	80,017	81,122
Loans and leases, net of unearned discount	349,970	382,384
Home equity lines and loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current	5,909,631	5,972,365
30-89 Days past due	36,408	40,537
Purchased impaired	2,564	2,617
Nonaccrual	85,122	78,516
Loans and leases, net of unearned discount	6,062,045	6,121,789
Automobile [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current	1,808,300	1,314,246
30-89 Days past due	24,692	29,144
Purchased impaired
Nonaccrual	17,417	21,144
Loans and leases, net of unearned discount	1,850,618	1,364,900
Other [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current	2,869,863	2,726,522
30-89 Days past due	34,863	47,830
Purchased impaired
Nonaccrual	16,341	25,087
Loans and leases, net of unearned discount	2,941,432	2,804,825
Non-Acquired [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
90 Days or more past due and accruing	312,990	368,510
Non-Acquired [Member] | Commercial, Financial, Leasing, etc. [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
90 Days or more past due and accruing	3,278	4,981
Non-Acquired [Member] | Commercial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
90 Days or more past due and accruing	36,688	63,353
Non-Acquired [Member] | Residential Builder and Developer [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
90 Days or more past due and accruing	1,615	141
Non-Acquired [Member] | Other commercial construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
90 Days or more past due and accruing	3,927
Non-Acquired [Member] | Residential [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
90 Days or more past due and accruing	263,529	294,649
Non-Acquired [Member] | Residential Alt-A [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
90 Days or more past due and accruing
Non-Acquired [Member] | Home equity lines and loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
90 Days or more past due and accruing
Non-Acquired [Member] | Automobile [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
90 Days or more past due and accruing
Non-Acquired [Member] | Other [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
90 Days or more past due and accruing	3,953	5,386
Acquired [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
90 Days or more past due and accruing	132,147	130,162
Acquired [Member] | Commercial, Financial, Leasing, etc. [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
90 Days or more past due and accruing	5,422	6,778
Acquired [Member] | Commercial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
90 Days or more past due and accruing	24,196	35,603
Acquired [Member] | Residential Builder and Developer [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
90 Days or more past due and accruing	13,786	7,930
Acquired [Member] | Other commercial construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
90 Days or more past due and accruing	1,516	8,031
Acquired [Member] | Residential [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
90 Days or more past due and accruing	42,286	43,700
Acquired [Member] | Residential Alt-A [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
90 Days or more past due and accruing
Acquired [Member] | Home equity lines and loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
90 Days or more past due and accruing	28,320	27,754
Acquired [Member] | Automobile [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
90 Days or more past due and accruing	209	366
Acquired [Member] | Other [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
90 Days or more past due and accruing	$ 16,412