Fair Value Accounting and Measurement (Carrying Amounts and Estimated Fair Values of Selected Financial Instruments) (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Assets
Interest-earning deposits with banks	$ 136,578	$ 31,200
Securities available for sale	2,207,873	2,278,577
Carrying (Reported) Amount, Fair Value Disclosure [Member]
Assets
Cash and due from banks	186,116	193,038
Interest-earning deposits with banks	136,578	31,200
Securities available for sale	2,207,873	2,278,577
FHLB stock	10,240	10,240
Loans held for sale	7,802	5,846
Loans	6,440,390	6,143,380
FDIC loss-sharing asset		3,535
Interest rate contracts	8,992	9,012
Liabilities
Deposits	8,341,717	8,059,415
FHLB Advances	6,465	6,493
Repurchase agreements	40,933	80,822
Interest rate contracts	9,004	9,036
Estimate of Fair Value, Fair Value Disclosure [Member]
Assets
Cash and due from banks	186,116	193,038
Interest-earning deposits with banks	136,578	31,200
Securities available for sale	2,207,873	2,278,577
FHLB stock	10,240	10,240
Loans held for sale	7,802	5,846
Loans	6,309,449	6,040,439
FDIC loss-sharing asset		867
Interest rate contracts	8,992	9,012
Liabilities
Deposits	8,337,145	8,055,168
FHLB Advances	7,367	7,070
Repurchase agreements	40,987	81,131
Interest rate contracts	9,004	9,036
Fair Value, Inputs, Level 1 [Member] \| Estimate of Fair Value, Fair Value Disclosure [Member]
Assets
Cash and due from banks	186,116	193,038
Interest-earning deposits with banks	136,578	31,200
Securities available for sale	250	800
FHLB stock	0	0
Loans held for sale	0	0
Loans	0	0
FDIC loss-sharing asset		0
Interest rate contracts	0	0
Liabilities
Deposits	7,960,870	7,653,122
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	2,207,623	2,277,777
FHLB stock	10,240	10,240
Loans held for sale	7,802	5,846
Loans	0	0
FDIC loss-sharing asset		0
Interest rate contracts	8,992	9,012
Liabilities
Deposits	376,275	402,046
FHLB Advances	7,367	7,070
Repurchase agreements	40,987	81,131
Interest rate contracts	9,004	9,036
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	6,309,449	6,040,439
FDIC loss-sharing asset		867
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.

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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

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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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
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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

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
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-URI http://asc.fasb.org/subtopic&trid=2196772

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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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-Paragraph 10
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