Loans and Leases (Loans and leases receivable) (Details) (USD $) In Thousands, unless otherwise specified											9 Months Ended				9 Months Ended				9 Months Ended
	Sep. 30, 2014	Dec. 31, 2013	Sep. 30, 2014 Commercial	Dec. 31, 2013 Commercial	Sep. 30, 2014 Commercial real estate	Dec. 31, 2013 Commercial real estate	Sep. 30, 2014 Agricultural and agricultural real estate	Dec. 31, 2013 Agricultural and agricultural real estate	Sep. 30, 2014 Commercial and Commercial Real Estate	Dec. 31, 2013 Commercial and Commercial Real Estate	Sep. 30, 2014 Commercial and Commercial Real Estate Minimum	Sep. 30, 2014 Commercial and Commercial Real Estate Maximum	Sep. 30, 2014 Residential real estate	Dec. 31, 2013 Residential real estate	Sep. 30, 2014 Residential real estate Minimum	Sep. 30, 2014 Residential real estate Maximum	Sep. 30, 2014 Consumer	Dec. 31, 2013 Consumer	Sep. 30, 2014 Consumer Citizens Finance Co Loans and Finance Receivables	Sep. 30, 2014 Gross Loans and Leases Receivable Held to Maturity	Dec. 31, 2013 Gross Loans and Leases Receivable Held to Maturity
Loans and Leases [Line Items]
Loans and leases receivable held to maturity	$ 3,800,424	$ 3,500,109	$ 1,024,712	$ 950,197	$ 1,684,832	$ 1,529,683	$ 404,423	$ 376,735	$ 2,709,544	$ 2,479,880			$ 360,309	$ 349,349			$ 326,148	$ 294,145		$ 3,800,424	$ 3,500,109
Unearned discount	(98)	(168)
Deferred loan fees	(2,021)	(2,989)
Total net loans and leases receivable held to maturity	3,798,305	3,496,952
Loans covered under loss share agreements	3,850	5,749					573	543	1,188	2,314			1,762	2,280			327	612
Allowance for loan and lease losses	(41,698)	(41,685)
Loans and leases receivable, net	$ 3,760,457	$ 3,461,016
Length of loan agreements											1 year	5 years			10 years	30 years
Concentration risk, percentage																			22.00%