Loans and Leases (Loans and leases receivable) (Details) (USD $)	3 Months Ended
Mar. 31, 2015	Dec. 31, 2014
Loans and Leases [Line Items]
Gross loans and leases receivable held to maturity	4,244,966,000us-gaap_NotesReceivableGross	$ 3,877,863,000us-gaap_NotesReceivableGross
Unearned discount	(85,000)	(90,000)
Deferred loan fees	(1,192,000)	(1,028,000)
Total net loans and leases receivable held to maturity	4,243,689,000	3,876,745,000
Total loans covered under loss share agreements	0	1,258,000
Allowance for loan and lease losses	(41,854,000)	(41,449,000)
Loans and leases receivable, net	4,201,835,000	3,836,554,000
Commercial
Loans and Leases [Line Items]
Gross loans and leases receivable held to maturity	1,134,614,000	1,036,080,000
Commercial real estate
Loans and Leases [Line Items]
Gross loans and leases receivable held to maturity	1,932,701,000	1,707,060,000
Agricultural and agricultural real estate
Loans and Leases [Line Items]
Gross loans and leases receivable held to maturity	411,732,000	423,827,000
Total loans covered under loss share agreements	0	0
Residential real estate
Loans and Leases [Line Items]
Gross loans and leases receivable held to maturity	413,938,000	380,341,000
Total loans covered under loss share agreements	0	1,204,000
Residential real estate \| Minimum
Loans and Leases [Line Items]
Length of loan agreements	10 years
Residential real estate \| Maximum
Loans and Leases [Line Items]
Length of loan agreements	30 years
Consumer
Loans and Leases [Line Items]
Gross loans and leases receivable held to maturity	351,981,000	330,555,000
Total loans covered under loss share agreements	0	0
Consumer \| Citizens Finance Co \| Loans and Finance Receivables
Loans and Leases [Line Items]
Concentration risk, percentage	21.00%
Gross loans and leases receivable held to maturity
Loans and Leases [Line Items]
Gross loans and leases receivable held to maturity	4,244,966,000	3,877,863,000
Commercial and commercial real estate
Loans and Leases [Line Items]
Gross loans and leases receivable held to maturity	3,067,315,000	2,743,140,000
Total loans covered under loss share agreements	0	$ 54,000
Commercial and commercial real estate \| Minimum
Loans and Leases [Line Items]
Length of loan agreements	1 year
Commercial and commercial real estate \| Maximum
Loans and Leases [Line Items]
Length of loan agreements	5 years

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Loans and Leases Receivable, Contract Term

+ References

No definition available.

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- Definition

For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 825

-SubTopic 10

-Section 50

-Paragraph 21

-Subparagraph (a)

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- Definition

Amount of allowance to cover probable credit losses on loans and leases. Includes carryover of or adjustments to the allowance for loan losses in connection with business combinations. Excludes allowance for loans and leases covered under loss sharing agreements.

+ 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 210.9-03.7(d))

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-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 7

-Subparagraph d

-Article 9

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-Publisher SEC

-Name Staff Accounting Bulletin (SAB)

-Number Topic 6

-Section L

-Subsection 1

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- Definition

Amount of deferred interest and fee income, unamortized costs incurred to originate loans and leases, unamortized loan commitments and loan syndication fees, and premiums over or discounts from face amounts of acquired loans. Excludes amounts for loans and leases covered under loss sharing agreements.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 10

-Section 50

-Paragraph 4

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-Publisher FASB

-Name Accounting Standards Codification

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- Definition

Aggregate gross carrying amount of loans and leases receivable covered by loss sharing agreements.

+ References

No definition available.

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- Definition

Amount before allowance and after deduction of deferred interest and fees, unamortized costs and premiums and discounts from face amounts, of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Excludes loans and leases covered under loss sharing agreements.

+ References

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- Definition

Amount after allowance and deduction of deferred interest and fees, unamortized costs and premiums over and discounts from face amounts, of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Includes loans and leases covered under loss sharing agreements.

+ References

No definition available.

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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

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- Definition

Amount of deferred fees paid by borrowers and unamortized costs incurred to originate loans and leases, unamortized loan commitments and loan syndication fees, and premiums over or discounts from face amounts of loans that are being amortized into income as an adjustment to yield. Excludes amounts for loans and leases covered under loss sharing agreements.

+ References

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