Loans and leases and the allowance for credit losses (Details 3) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Changes in the allowance for credit losses
Beginning balance	$ 909,006	$ 903,703	$ 908,290	$ 902,941
Provision for credit losses	60,000	63,000	109,000	138,000
Net charge-offs
Charge-offs	(64,162)	(71,650)	(124,438)	(154,744)
Recoveries	12,184	12,536	24,176	21,392
Net charge-offs	(51,978)	(59,114)	(100,262)	(133,352)
Ending balance	917,028	907,589	917,028	907,589
Commercial, financial, leasing [Member]
Changes in the allowance for credit losses
Beginning balance	239,273	215,659	234,022	212,579
Provision for credit losses	19,103	6,870	29,224	21,812
Net charge-offs
Charge-offs	(16,078)	(14,923)	(24,115)	(28,950)
Recoveries	2,430	2,273	5,597	4,438
Net charge-offs	(13,648)	(12,650)	(18,518)	(24,512)
Ending balance	244,728	209,879	244,728	209,879
Real Estate Commercial [Member]
Changes in the allowance for credit losses
Beginning balance	356,554	391,107	367,637	400,562
Provision for credit losses	(3,309)	22,735	(5,569)	37,510
Net charge-offs
Charge-offs	(13,056)	(15,915)	(23,596)	(40,494)
Recoveries	1,332	3,184	3,049	3,533
Net charge-offs	(11,724)	(12,731)	(20,547)	(36,961)
Ending balance	341,521	401,111	341,521	401,111
Residential real estate [Member]
Changes in the allowance for credit losses
Beginning balance	97,301	87,526	91,915	86,351
Provision for credit losses	5,587	13,654	21,817	29,495
Net charge-offs
Charge-offs	(11,407)	(15,872)	(24,125)	(32,039)
Recoveries	1,788	2,033	3,662	3,534
Net charge-offs	(9,619)	(13,839)	(20,463)	(28,505)
Ending balance	93,269	87,341	93,269	87,341
Consumer [Member]
Changes in the allowance for credit losses
Beginning balance	142,912	137,351	143,121	133,067
Provision for credit losses	38,427	19,852	61,965	47,616
Net charge-offs
Charge-offs	(23,621)	(24,940)	(52,602)	(53,261)
Recoveries	6,634	5,046	11,868	9,887
Net charge-offs	(16,987)	(19,894)	(40,734)	(43,374)
Ending balance	164,352	137,309	164,352	137,309
Unallocated [Member]
Changes in the allowance for credit losses
Beginning balance	72,966	72,060	71,595	70,382
Provision for credit losses	192	(111)	1,563	1,567
Net charge-offs
Charge-offs
Recoveries
Net charge-offs
Ending balance	$ 73,158	$ 71,949	$ 73,158	$ 71,949