Loans and leases and the allowance for credit losses (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
Outstanding principal and carrying value of acquired loans recorded at fair value
Outstanding principal balance	$ 8,097,216	$ 9,203,366
Carrying amount	7,088,438	8,159,787
Commercial, financial, leasing [Member]
Outstanding principal and carrying value of acquired loans recorded at fair value
Carrying amount	1,216,711	1,331,198
Commercial real estate [Member]
Outstanding principal and carrying value of acquired loans recorded at fair value
Carrying amount	3,222,688	3,879,518
Residential real estate [Member]
Outstanding principal and carrying value of acquired loans recorded at fair value
Carrying amount	814,288	915,371
Consumer [Member]
Outstanding principal and carrying value of acquired loans recorded at fair value
Carrying amount	$ 1,834,751	$ 2,033,700