Fair Value Accounting and Measurement (Carrying Amounts and Estimated Fair Values of Selected Financial Instruments) (Details) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Assets
Interest-earning deposits with banks	$ 11,225	$ 8,373
Securities available for sale	2,360,084	2,157,694
Carrying (Reported) Amount, Fair Value Disclosure [Member]
Assets
Cash and due from banks	180,839	166,929
Interest-earning deposits with banks	11,225	8,373
Securities available for sale	2,360,084	2,157,694
FHLB stock	12,640	12,722
Loans held for sale	3,361	4,509
Loans	6,189,493	5,746,855
FDIC loss-sharing asset	3,592	6,568
Interest rate contracts	19,803	12,438
Liabilities
Deposits	8,057,816	7,438,829
FHLB Advances	66,502	68,531
Repurchase agreements	69,189	99,699
Interest rate contracts	19,841	12,478
Estimate of Fair Value, Fair Value Disclosure [Member]
Assets
Cash and due from banks	180,839	166,929
Interest-earning deposits with banks	11,225	8,373
Securities available for sale	2,360,084	2,157,694
FHLB stock	12,640	12,722
Loans held for sale	3,361	4,509
Loans	6,274,917	5,752,423
FDIC loss-sharing asset	594	921
Interest rate contracts	19,803	12,438
Liabilities
Deposits	8,054,970	7,434,787
FHLB Advances	67,826	69,176
Repurchase agreements	69,543	100,346
Interest rate contracts	19,841	12,478
Fair Value, Inputs, Level 1 [Member] \| Estimate of Fair Value, Fair Value Disclosure [Member]
Assets
Cash and due from banks	180,839	166,929
Interest-earning deposits with banks	11,225	8,373
Securities available for sale	548	20,137
FHLB stock	0	0
Loans held for sale	0	0
Loans	0	0
FDIC loss-sharing asset	0	0
Interest rate contracts	0	0
Liabilities
Deposits	7,645,310	6,979,924
FHLB Advances	0	0
Repurchase agreements	0	0
Interest rate contracts	0	0
Fair Value, Inputs, Level 2 [Member] \| Estimate of Fair Value, Fair Value Disclosure [Member]
Assets
Cash and due from banks	0	0
Interest-earning deposits with banks	0	0
Securities available for sale	2,359,536	2,137,557
FHLB stock	12,640	12,722
Loans held for sale	3,361	4,509
Loans	0	0
FDIC loss-sharing asset	0	0
Interest rate contracts	19,803	12,438
Liabilities
Deposits	409,660	454,863
FHLB Advances	67,826	69,176
Repurchase agreements	69,543	100,346
Interest rate contracts	19,841	12,478
Fair Value, Inputs, Level 3 [Member] \| Estimate of Fair Value, Fair Value Disclosure [Member]
Assets
Cash and due from banks	0	0
Interest-earning deposits with banks	0	0
Securities available for sale	0	0
FHLB stock	0	0
Loans held for sale	0	0
Loans	6,274,917	5,752,423
FDIC loss-sharing asset	594	921
Interest rate contracts	0	0
Liabilities
Deposits	0	0
FHLB Advances	0	0
Repurchase agreements	0	0
Interest rate contracts	$ 0	$ 0

FDIC Loss Sharing Asset Fair Value Disclosure

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- Definition

Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 25
-Paragraph 1
-Subparagraph (b)
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Fair value portion of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Cash
-URI http://asc.fasb.org/extlink&oid=6506951

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-Name Accounting Standards Codification
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Fair value portion of deposit liabilities held by the entity, including, but not limited to, foreign and domestic, interest and noninterest bearing, demand deposits, saving deposits, negotiable orders of withdrawal (NOW) and time deposits.

+ References

No definition available.

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- Definition

Fair value portion of borrowing from Federal Home Loan Bank (FHLBank).

+ References

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- References

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For banks and other depository institutions (including Federal Reserve Banks, if applicable): Interest-bearing deposits in other financial institutions for relatively short periods of time including, for example, certificates of deposits, which are presented separately from cash on the balance sheet.

+ 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 210.9-03.2)
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- Definition

Fair value as of the balance sheet date of interest rate derivative assets, which includes all such derivative instruments in hedging and nonhedging relationships that are recognized as assets.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 10
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Fair value as of the balance sheet date of interest rate derivative liabilities, which includes all such derivative instruments in hedging and nonhedging relationships that are recognized as liabilities.

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Fair value portion of investments in Federal Home Loan Bank (FHLBank) stock.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 325
-SubTopic 20
-Section 25
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=29638263&loc=d3e39828-111592

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- Definition

Fair value portion of loans held-for-sale including, but not limited to, mortgage loans and finance receivables.

+ References

No definition available.

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Fair value portion of loan receivable, including, but not limited to, mortgage loans held for investment, finance receivables held for investment, policy loans on insurance contracts.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Glossary Loan
-URI http://asc.fasb.org/extlink&oid=6517073

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- Definition

Fair value portion of securities that an entity sells and agrees to repurchase at a specified date for a specified price.

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-Publisher FASB
-Name Accounting Standards Codification
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