Loans and Leases (Loans and Leases Not Covered by Share Agreements (Past Due Financing Receivables)) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-59 Days Past Due	$ 6,306	$ 8,380
60-89 Days Past Due	2,020	2,085
90 Days or More Past Due	0	24
Total Past Due	8,326	10,489
Current	3,844,467	3,447,226
Nonaccrual	25,070	42,394
Total	3,877,863us-gaap_NotesReceivableGross	3,500,109us-gaap_NotesReceivableGross
Commercial
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-59 Days Past Due	980	697
60-89 Days Past Due	48	741
90 Days or More Past Due	0	0
Total Past Due	1,028	1,438
Current	1,032,707	935,508
Nonaccrual	2,345	13,251
Total	1,036,080	950,197
Commercial Real Estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-59 Days Past Due	1,788	3,042
60-89 Days Past Due	111	199
90 Days or More Past Due	0	24
Total Past Due	1,899	3,265
Current	1,693,554	1,511,618
Nonaccrual	11,607	14,800
Total	1,707,060	1,529,683
Commercial and Commercial Real Estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-59 Days Past Due	2,768	3,739
60-89 Days Past Due	159	940
90 Days or More Past Due	0	24
Total Past Due	2,927	4,703
Current	2,726,261	2,447,126
Nonaccrual	13,952	28,051
Total	2,743,140	2,479,880
Agricultural and Agricultural Real Estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-59 Days Past Due	119	818
60-89 Days Past Due	50	0
90 Days or More Past Due	0	0
Total Past Due	169	818
Current	422,219	369,907
Nonaccrual	1,439	6,010
Total	423,827	376,735
Residential Real Estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-59 Days Past Due	1,037	1,199
60-89 Days Past Due	445	56
90 Days or More Past Due	0	0
Total Past Due	1,482	1,255
Current	371,982	342,735
Nonaccrual	6,877	5,359
Total	380,341	349,349
Consumer
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-59 Days Past Due	2,382	2,624
60-89 Days Past Due	1,366	1,089
90 Days or More Past Due	0	0
Total Past Due	3,748	3,713
Current	324,005	287,458
Nonaccrual	2,802	2,974
Total	$ 330,555	$ 294,145

Financing receivables that are less than 60 days past due but more than 29 days past due.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 10

-Section 50

-Paragraph 7A

-URI http://asc.fasb.org/extlink&oid=35738203&loc=SL6953401-111524

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Financing receivables that are less than 90 days past due but more than 59 days past due.

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- Definition

Recorded investment in financing receivables that are 90 days or more past due and still accruing.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 10

-Section 50

-Paragraph 7

-Subparagraph (d)

-URI http://asc.fasb.org/extlink&oid=35738203&loc=d3e5111-111524

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Financing receivables that are current.

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Recorded investment in financing receivables that are on nonaccrual status as of the balance sheet date.

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Recorded Investment in financing receivables that are past due at the balance sheet date.

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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

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