Loans and leases - Summary of Current, Past Due and Nonaccrual Loans (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Loans And Leases Receivable [Line Items]
Current	$ 63,854,815	$ 57,167,794
30-89 Days Past Due	730,901	725,654
Purchased Impaired	447,114	653,362
Nonaccrual	1,013,176	1,097,581
Total	66,570,957	60,096,005
Commercial, Financial, Leasing, etc [Member]
Loans And Leases Receivable [Line Items]
Current	17,511,052	15,493,803
30-89 Days Past Due	62,479	37,112
Purchased Impaired	17,437	23,762
Nonaccrual	151,908	163,598
Total	17,776,953	15,734,436
Commercial [Member]
Loans And Leases Receivable [Line Items]
Current	21,759,997	19,658,761
30-89 Days Past Due	118,249	172,641
Purchased Impaired	132,962	192,804
Nonaccrual	193,859	171,111
Total	22,273,173	20,259,448
Residential Builder and Developer [Member]
Loans And Leases Receivable [Line Items]
Current	757,311	845,680
30-89 Days Past Due	35,419	49,353
Purchased Impaired	187,764	297,005
Nonaccrual	181,865	281,576
Total	1,189,526	1,508,333
Other Commercial Construction [Member]
Loans And Leases Receivable [Line Items]
Current	2,379,953	2,393,304
30-89 Days Past Due	35,274	41,049
Purchased Impaired	68,971	78,105
Nonaccrual	36,812	106,325
Total	2,531,091	2,643,333
Residential [Member]
Loans And Leases Receivable [Line Items]
Current	9,811,956	6,626,182
30-89 Days Past Due	337,969	256,017
Purchased Impaired	36,769	56,741
Nonaccrual	249,314	172,681
Total	10,794,316	7,400,075
Residential Alt-A [Member]
Loans And Leases Receivable [Line Items]
Current	331,021	383,834
30-89 Days Past Due	19,692	34,077
Purchased Impaired
Nonaccrual	95,808	105,179
Total	446,521	523,090
Home equity lines and loans [Member]
Loans And Leases Receivable [Line Items]
Current	6,199,591	6,570,675
30-89 Days Past Due	40,759	43,516
Purchased Impaired	3,211	4,635
Nonaccrual	58,071	47,150
Total	6,321,950	6,681,385
Automobile [Member]
Loans And Leases Receivable [Line Items]
Current	2,442,502	2,644,330
30-89 Days Past Due	40,461	48,342
Purchased Impaired
Nonaccrual	25,107	26,835
Total	2,508,321	2,720,108
Other [Member]
Loans And Leases Receivable [Line Items]
Current	2,661,432	2,551,225
30-89 Days Past Due	40,599	43,547
Purchased Impaired		310
Nonaccrual	20,432	23,126
Total	2,729,106	2,625,797
Non-acquired [Member]
Loans And Leases Receivable [Line Items]
90 Days or More Past Due and Accruing	358,397	287,876
Non-acquired [Member] | Commercial, Financial, Leasing, etc [Member]
Loans And Leases Receivable [Line Items]
90 Days or More Past Due and Accruing	23,490	7,601
Non-acquired [Member] | Commercial [Member]
Loans And Leases Receivable [Line Items]
90 Days or More Past Due and Accruing	13,111	9,983
Non-acquired [Member] | Residential Builder and Developer [Member]
Loans And Leases Receivable [Line Items]
90 Days or More Past Due and Accruing	3,258	13,603
Non-acquired [Member] | Other Commercial Construction [Member]
Loans And Leases Receivable [Line Items]
90 Days or More Past Due and Accruing	509	968
Non-acquired [Member] | Residential [Member]
Loans And Leases Receivable [Line Items]
90 Days or More Past Due and Accruing	313,184	250,472
Non-acquired [Member] | Residential Alt-A [Member]
Loans And Leases Receivable [Line Items]
90 Days or More Past Due and Accruing
Non-acquired [Member] | Home equity lines and loans [Member]
Loans And Leases Receivable [Line Items]
90 Days or More Past Due and Accruing
Non-acquired [Member] | Automobile [Member]
Loans And Leases Receivable [Line Items]
90 Days or More Past Due and Accruing
Non-acquired [Member] | Other [Member]
Loans And Leases Receivable [Line Items]
90 Days or More Past Due and Accruing	4,845	5,249
Acquired [Member]
Loans And Leases Receivable [Line Items]
90 Days or More Past Due and Accruing	166,554	163,738
Acquired [Member] | Commercial, Financial, Leasing, etc [Member]
Loans And Leases Receivable [Line Items]
90 Days or More Past Due and Accruing	10,587	8,560
Acquired [Member] | Commercial [Member]
Loans And Leases Receivable [Line Items]
90 Days or More Past Due and Accruing	54,995	54,148
Acquired [Member] | Residential Builder and Developer [Member]
Loans And Leases Receivable [Line Items]
90 Days or More Past Due and Accruing	23,909	21,116
Acquired [Member] | Other Commercial Construction [Member]
Loans And Leases Receivable [Line Items]
90 Days or More Past Due and Accruing	9,572	23,582
Acquired [Member] | Residential [Member]
Loans And Leases Receivable [Line Items]
90 Days or More Past Due and Accruing	45,124	37,982
Acquired [Member] | Residential Alt-A [Member]
Loans And Leases Receivable [Line Items]
90 Days or More Past Due and Accruing
Acquired [Member] | Home equity lines and loans [Member]
Loans And Leases Receivable [Line Items]
90 Days or More Past Due and Accruing	20,318	15,409
Acquired [Member] | Automobile [Member]
Loans And Leases Receivable [Line Items]
90 Days or More Past Due and Accruing	251	601
Acquired [Member] | Other [Member]
Loans And Leases Receivable [Line Items]
90 Days or More Past Due and Accruing	$ 1,798	$ 2,340