Loans and leases and the allowance for credit losses (Details 1) (USD $) In Thousands, unless otherwise specified	3 Months Ended	6 Months Ended
	Jun. 30, 2012	Jun. 30, 2012
Summary of changes in Accretable Yield for acquired loans
Balance at the beginning of period	$ 770,031	$ 838,765
Interest income	(89,870)	(171,257)
Reclassifications from (to) nonaccretable balance, net	139,820	140,244
Other (a)	(31,221)	(18,992)
Balance at end of period	788,760	788,760
Other [Member]
Summary of changes in Accretable Yield for acquired loans
Balance at the beginning of period	747,466	807,960
Interest income	(80,249)	(153,972)
Reclassifications from (to) nonaccretable balance, net	97,165	98,165
Other (a)	(31,221)	(18,992)
Balance at end of period	733,161	733,161
Purchase Impaired [Member]
Summary of changes in Accretable Yield for acquired loans
Balance at the beginning of period	22,565	30,805
Interest income	(9,621)	(17,285)
Reclassifications from (to) nonaccretable balance, net	42,655	42,079
Balance at end of period	$ 55,599	$ 55,599