Loans and Leases (Loans and Leases Not Covered by Share Agreements (Credit Quality Indicator)) (Details) (USD $)	Dec. 31, 2014 loans	Dec. 31, 2013 loans
Financing Receivable, Recorded Investment [Line Items]
Number of loans classified as doubtful	0
Number of loans classified as loss	0
Loans and leases receivable	$ 3,877,863,000us-gaap_NotesReceivableGross	$ 3,500,109,000us-gaap_NotesReceivableGross
Number of loans classified as doubtful on nonaccrual status		1
Loans delinquent 30-89 days as a percentage of total loans	0.21%	0.30%
Pass
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivable	3,592,750,000	3,215,775,000
Nonpass
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivable	285,113,000	284,334,000
Nonimpaired Purchased Loans
Financing Receivable, Recorded Investment [Line Items]
Doubtful loan, specific reserve		2,200,000
Commercial
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivable	1,036,080,000	950,197,000
Commercial \| Pass
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivable	939,717,000	871,825,000
Commercial \| Nonpass
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivable	96,363,000	78,372,000
Commercial Real Estate
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivable	1,707,060,000	1,529,683,000
Commercial Real Estate \| Pass
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivable	1,567,711,000	1,390,820,000
Commercial Real Estate \| Nonpass
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivable	139,349,000	138,863,000
Commercial and Commercial Real Estate
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivable	2,743,140,000	2,479,880,000
Commercial and Commercial Real Estate \| Pass
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivable	2,507,428,000	2,262,645,000
Commercial and Commercial Real Estate \| Nonpass
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivable	235,712,000	217,235,000
Agricultural and Agricultural Real Estate
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivable	423,827,000	376,735,000
Agricultural and Agricultural Real Estate \| Pass
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivable	402,883,000	335,821,000
Agricultural and Agricultural Real Estate \| Nonpass
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivable	20,944,000	40,914,000
Residential Real Estate
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivable	380,341,000	349,349,000
Residential Real Estate \| Pass
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivable	361,325,000	333,161,000
Residential Real Estate \| Nonpass
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivable	19,016,000	16,188,000
Consumer
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivable	330,555,000	294,145,000
Consumer \| Pass
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivable	321,114,000	284,148,000
Consumer \| Nonpass
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivable	$ 9,441,000	$ 9,997,000

Financing Receivable, Recorded Investment, 30 to 89 Days Past Due, Percentage

No definition available.

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- Definition

Internal Credit Quality Indicator Doubtful, Number of Loans

+ References

No definition available.

+ Details

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- Definition

Internal Credit Quality Indicator Doubtful, Number of Loans, Nonaccrual Status

+ References

No definition available.

+ Details

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- Definition

Internal Credit Quality Indicator Loss, Number of Loans

+ References

No definition available.

+ Details

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- Details

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- Definition

Amount of allowance for credit losses related to recorded investment.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 10

-Section 50

-Paragraph 15

-Subparagraph (a)(3)

-URI http://asc.fasb.org/extlink&oid=35738203&loc=d3e5212-111524

+ Details

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- Definition

Amount representing an agreement for an unconditional promise by the maker to pay the entity (holder) a definite sum of money at a future date. Such amount may include accrued interest receivable in accordance with the terms of the note. The note also may contain provisions and related items including a discount or premium, payable on demand, secured, or unsecured, interest bearing or noninterest bearing, among a myriad of other features and characteristics. Excludes amounts related to receivables held-for-sale.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.9-03.10(3))

-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 10

-Subparagraph 3

-Article 9

+ Details

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- Details

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