Loans and leases (Details 4) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011 Modification
Loan modification activities that were considered troubled debt restructurings
Number of modifications	1,780
Pre-modification Recorded Investment	$ 332,160
Post-modification Recorded Investment	313,827
Financial effects of modification recorded investment	(18,333)
Financial effects of modification interest	(6,338)
Other [Member]
Loan modification activities that were considered troubled debt restructurings
Number of modifications	4
Pre-modification Recorded Investment	103
Post-modification Recorded Investment	103
Principal deferral [Member] | Commercial, financial, leasing, etc. [Member]
Loan modification activities that were considered troubled debt restructurings
Number of modifications	53
Pre-modification Recorded Investment	10,703
Post-modification Recorded Investment	10,778
Financial effects of modification recorded investment	75
Principal deferral [Member] | Commercial real estate loans [Member]
Loan modification activities that were considered troubled debt restructurings
Number of modifications	29
Pre-modification Recorded Investment	16,804
Post-modification Recorded Investment	16,704
Financial effects of modification recorded investment	(100)
Principal deferral [Member] | Residential builder and developer [Member]
Loan modification activities that were considered troubled debt restructurings
Number of modifications	9
Pre-modification Recorded Investment	33,208
Post-modification Recorded Investment	26,811
Financial effects of modification recorded investment	(6,397)
Principal deferral [Member] | Other commercial construction [Member]
Loan modification activities that were considered troubled debt restructurings
Number of modifications	3
Pre-modification Recorded Investment	8,436
Post-modification Recorded Investment	8,553
Financial effects of modification recorded investment	117
Principal deferral [Member] | Residential real estate excluding Alt-A [Member]
Loan modification activities that were considered troubled debt restructurings
Number of modifications	37
Pre-modification Recorded Investment	8,175
Post-modification Recorded Investment	8,235
Financial effects of modification recorded investment	60
Principal deferral [Member] | Residential Alt-A [Member]
Loan modification activities that were considered troubled debt restructurings
Number of modifications	3
Pre-modification Recorded Investment	800
Post-modification Recorded Investment	835
Financial effects of modification recorded investment	35
Principal deferral [Member] | Home equity lines and loans [Member]
Loan modification activities that were considered troubled debt restructurings
Number of modifications	3
Pre-modification Recorded Investment	259
Post-modification Recorded Investment	259
Principal deferral [Member] | Automobile [Member]
Loan modification activities that were considered troubled debt restructurings
Number of modifications	746
Pre-modification Recorded Investment	10,053
Post-modification Recorded Investment	10,053
Principal deferral [Member] | Other [Member]
Loan modification activities that were considered troubled debt restructurings
Number of modifications	23
Pre-modification Recorded Investment	400
Post-modification Recorded Investment	400
Other [Member] | Residential builder and developer [Member]
Loan modification activities that were considered troubled debt restructurings
Number of modifications	6
Pre-modification Recorded Investment	118,114
Post-modification Recorded Investment	110,156
Financial effects of modification recorded investment	(7,958)
Other [Member] | Home equity lines and loans [Member]
Loan modification activities that were considered troubled debt restructurings
Number of modifications	3
Pre-modification Recorded Investment	86
Post-modification Recorded Investment	86
Other [Member] | Automobile [Member]
Loan modification activities that were considered troubled debt restructurings
Number of modifications	111
Pre-modification Recorded Investment	739
Post-modification Recorded Investment	739
Interest Rate Reduction [Member] | Residential real estate excluding Alt-A [Member]
Loan modification activities that were considered troubled debt restructurings
Number of modifications	14
Pre-modification Recorded Investment	1,926
Post-modification Recorded Investment	1,991
Financial effects of modification recorded investment	65
Financial effects of modification interest	(318)
Interest Rate Reduction [Member] | Automobile [Member]
Loan modification activities that were considered troubled debt restructurings
Number of modifications	17
Pre-modification Recorded Investment	183
Post-modification Recorded Investment	183
Financial effects of modification interest	(13)
Interest Rate Reduction [Member] | Other [Member]
Loan modification activities that were considered troubled debt restructurings
Number of modifications	1
Pre-modification Recorded Investment	8
Post-modification Recorded Investment	8
Financial effects of modification interest	(1)
Combination of concession types [Member] | Commercial, financial, leasing, etc. [Member]
Loan modification activities that were considered troubled debt restructurings
Number of modifications	3
Pre-modification Recorded Investment	2,049
Post-modification Recorded Investment	2,046
Financial effects of modification recorded investment	(3)
Financial effects of modification interest	(654)
Combination of concession types [Member] | Commercial real estate loans [Member]
Loan modification activities that were considered troubled debt restructurings
Number of modifications	3
Pre-modification Recorded Investment	15,778
Post-modification Recorded Investment	15,777
Financial effects of modification recorded investment	(1)
Financial effects of modification interest	(1,463)
Combination of concession types [Member] | Residential builder and developer [Member]
Loan modification activities that were considered troubled debt restructurings
Number of modifications	5
Pre-modification Recorded Investment	2,540
Post-modification Recorded Investment	2,561
Financial effects of modification recorded investment	21
Combination of concession types [Member] | Other commercial construction [Member]
Loan modification activities that were considered troubled debt restructurings
Number of modifications	3
Pre-modification Recorded Investment	65,813
Post-modification Recorded Investment	60,973
Financial effects of modification recorded investment	(4,840)
Combination of concession types [Member] | Residential real estate excluding Alt-A [Member]
Loan modification activities that were considered troubled debt restructurings
Number of modifications	111
Pre-modification Recorded Investment	19,508
Post-modification Recorded Investment	19,934
Financial effects of modification recorded investment	426
Financial effects of modification interest	(1,559)
Combination of concession types [Member] | Residential Alt-A [Member]
Loan modification activities that were considered troubled debt restructurings
Number of modifications	34
Pre-modification Recorded Investment	6,813
Post-modification Recorded Investment	6,978
Financial effects of modification recorded investment	165
Financial effects of modification interest	(889)
Combination of concession types [Member] | Home equity lines and loans [Member]
Loan modification activities that were considered troubled debt restructurings
Number of modifications	26
Pre-modification Recorded Investment	2,156
Post-modification Recorded Investment	2,158
Financial effects of modification recorded investment	2
Financial effects of modification interest	(444)
Combination of concession types [Member] | Automobile [Member]
Loan modification activities that were considered troubled debt restructurings
Number of modifications	431
Pre-modification Recorded Investment	6,703
Post-modification Recorded Investment	6,703
Financial effects of modification interest	(808)
Combination of concession types [Member] | Other [Member]
Loan modification activities that were considered troubled debt restructurings
Number of modifications	102
Pre-modification Recorded Investment	803
Post-modification Recorded Investment	803
Financial effects of modification interest	$ (189)