Fair Value Accounting and Measurement (Carrying Amounts and Estimated Fair Values of Selected Financial Instruments) (Details) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
Assets
Interest-earning deposits with banks	$ 5,564	$ 16,949
Securities available for sale	1,914,445	2,098,257
Carrying (Reported) Amount, Fair Value Disclosure [Member]
Assets
Cash and due from banks	172,139	171,221
Interest-earning deposits with banks	5,564	16,949
Securities available for sale	1,914,445	2,098,257
FHLB stock	11,803	33,365
Loans held for sale	4,220	1,116
Loans	5,542,640	5,375,809
FDIC loss-sharing asset	9,344	15,174
Interest rate contracts	10,659	11,800
Liabilities
Deposits	7,044,373	6,924,722
FHLB Advances	45,549	216,568
Repurchase agreements	92,230	105,080
Interest rate contracts	10,707	11,851
Estimate of Fair Value, Fair Value Disclosure [Member]
Assets
Cash and due from banks	172,139	171,221
Interest-earning deposits with banks	5,564	16,949
Securities available for sale	1,914,445	2,098,257
FHLB stock	11,803	33,365
Loans held for sale	4,220	1,116
Loans	5,624,212	5,516,286
FDIC loss-sharing asset	1,356	4,054
Interest rate contracts	10,659	11,800
Liabilities
Deposits	7,041,949	6,921,804
FHLB Advances	46,057	217,296
Repurchase agreements	93,175	106,171
Interest rate contracts	10,707	11,851
Fair Value, Inputs, Level 1 [Member] \| Estimate of Fair Value, Fair Value Disclosure [Member]
Assets
Cash and due from banks	172,139	171,221
Interest-earning deposits with banks	5,564	16,949
Securities available for sale	20,162	20,499
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	6,562,670	6,416,017
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	1,894,283	2,077,758
FHLB stock	11,803	33,365
Loans held for sale	4,220	1,116
Loans	0	0
FDIC loss-sharing asset	0	0
Interest rate contracts	10,659	11,800
Liabilities
Deposits	479,279	505,787
FHLB Advances	46,057	217,296
Repurchase agreements	93,175	106,171
Interest rate contracts	10,707	11,851
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	5,624,212	5,516,286
FDIC loss-sharing asset	1,356	4,054
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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Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

+ References

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-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.

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-Publisher FASB

-Name Accounting Standards Codification

-Glossary Cash

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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).

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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

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.9-03.2)

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-Section 45

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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

-Subparagraph (a)

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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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-Publisher FASB

-Name Accounting Standards Codification

-Topic 325

-SubTopic 20

-Section 25

-Paragraph 1

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

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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

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 10

-Glossary Loan

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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

-Topic 825

-SubTopic 10

-Section 50

-Paragraph 10

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