Allowance for Loan and Lease Losses (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Balance at beginning of year				$ 38,715				$ 36,808	$ 38,715	$ 36,808	$ 42,693
Provision for loan and lease losses	2,049	5,149	1,862	637	3,350	(502)	3,000	2,354	9,697	8,202	29,365
Recoveries on loans and leases previously charged-off									4,820	8,209	4,730
Loans and leases charged-off									(11,547)	(14,504)	(39,980)
Balance at end of year	41,685				38,715				41,685	38,715	36,808
Commercial
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Balance at beginning of year				11,388				10,549	11,388	10,549
Provision for loan and lease losses									3,152	672
Recoveries on loans and leases previously charged-off									1,019	1,966
Loans and leases charged-off									(2,460)	(1,799)
Balance at end of year	13,099				11,388				13,099	11,388
Commercial Real Estate
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Balance at beginning of year				14,473				14,621	14,473	14,621
Provision for loan and lease losses									552	1,556
Recoveries on loans and leases previously charged-off									2,378	5,194
Loans and leases charged-off									(3,251)	(6,898)
Balance at end of year	14,152				14,473				14,152	14,473
Agricultural
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Balance at beginning of year				2,138				1,763	2,138	1,763
Provision for loan and lease losses									767	295
Recoveries on loans and leases previously charged-off									110	81
Loans and leases charged-off									(23)	(1)
Balance at end of year	2,992				2,138				2,992	2,138
Residential Real Estate
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Balance at beginning of year				3,543				3,001	3,543	3,001
Provision for loan and lease losses									1,055	1,366
Recoveries on loans and leases previously charged-off									158	164
Loans and leases charged-off									(1,036)	(988)
Balance at end of year	3,720				3,543				3,720	3,543
Consumer
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Balance at beginning of year				7,173				6,874	7,173	6,874
Provision for loan and lease losses									4,171	4,313
Recoveries on loans and leases previously charged-off									1,155	804
Loans and leases charged-off									(4,777)	(4,818)
Balance at end of year	7,722				7,173				7,722	7,173
Unallocated
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Balance at beginning of year				0				0	0	0
Provision for loan and lease losses									0	0
Recoveries on loans and leases previously charged-off									0	0
Loans and leases charged-off									0	0
Balance at end of year	$ 0				$ 0				$ 0	$ 0