Loans and leases and the allowance for credit losses (Details 3) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Changes in the allowance for credit losses
Beginning balance	$ 908,290	$ 902,941
Provision for credit losses	49,000	75,000
Net charge-offs
Charge-offs	(60,276)	(83,094)
Recoveries	11,992	8,856
Net charge-offs	(48,284)	(74,238)
Ending balance	909,006	903,703
Commercial, financial, leasing, etc. [Member]
Changes in the allowance for credit losses
Beginning balance	234,022	212,579
Provision for credit losses	10,121	14,942
Net charge-offs
Charge-offs	(8,037)	(14,027)
Recoveries	3,167	2,165
Net charge-offs	(4,870)	(11,862)
Ending balance	239,273	215,659
Real Estate Commercial [Member]
Changes in the allowance for credit losses
Beginning balance	367,637	400,562
Provision for credit losses	(2,260)	14,775
Net charge-offs
Charge-offs	(10,540)	(24,579)
Recoveries	1,717	349
Net charge-offs	(8,823)	(24,230)
Ending balance	356,554	391,107
Residential real estate [Member]
Changes in the allowance for credit losses
Beginning balance	91,915	86,351
Provision for credit losses	16,230	15,841
Net charge-offs
Charge-offs	(12,718)	(16,167)
Recoveries	1,874	1,501
Net charge-offs	(10,844)	(14,666)
Ending balance	97,301	87,526
Consumer [Member]
Changes in the allowance for credit losses
Beginning balance	143,121	133,067
Provision for credit losses	23,538	27,764
Net charge-offs
Charge-offs	(28,981)	(28,321)
Recoveries	5,234	4,841
Net charge-offs	(23,747)	(23,480)
Ending balance	142,912	137,351
Unallocated [Member]
Changes in the allowance for credit losses
Beginning balance	71,595	70,382
Provision for credit losses	1,371	1,678
Net charge-offs
Ending balance	$ 72,966	$ 72,060