Fair Value Measurements and Fair Value of Financial Instruments, Estimated Fair Values of Financial Instruments (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Financial assets [Abstract]
HTM securities	$ 495,411	$ 525,050
Financial liabilities [Abstract]
Time deposits	776,756	872,411
Long-term debt	88,914	104,087
Junior subordinated debt	101,196	101,196
Carrying Amount [Member] \| Level 2 [Member]
Financial assets [Abstract]
HTM securities	494,309	527,948
Financial liabilities [Abstract]
Time deposits	776,756	872,411
Long-term debt	88,914	104,087
Junior subordinated debt	101,196	101,196
Carrying Amount [Member] \| Level 3 [Member]
Financial assets [Abstract]
Net loans	6,398,584	6,132,857
Estimated Fair Value [Member] \| Level 2 [Member]
Financial assets [Abstract]
HTM securities	495,411	525,050
Financial liabilities [Abstract]
Time deposits	773,160	868,153
Long-term debt	88,948	104,113
Junior subordinated debt	104,584	102,262
Estimated Fair Value [Member] \| Level 3 [Member]
Financial assets [Abstract]
Net loans	6,557,674	6,273,233
Not Designated as Hedging Instrument [Member] \| Interest Rate Swaps [Member] \| Other Assets [Member]
Derivatives, Fair Value [Line Items]
Derivative asset, notional amount	469,800	371,100
Fair value of derivative asset	3,900	300
Not Designated as Hedging Instrument [Member] \| Interest Rate Swaps [Member] \| Other Liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative liability, notional amount	469,800	371,100
Fair value of derivative liability	3,900	300
Designated as Hedging Instrument [Member] \| Cash Flow Hedging [Member] \| Interest Rate Swaps [Member]
Derivatives, Fair Value [Line Items]
Notional amount	250,000	250,000
Designated as Hedging Instrument [Member] \| Cash Flow Hedging [Member] \| Interest Rate Swaps [Member] \| Other Assets [Member]
Derivatives, Fair Value [Line Items]
Fair value of derivative asset	2,700	2,900
Designated as Hedging Instrument [Member] \| Cash Flow Hedging [Member] \| Interest Rate Swaps [Member] \| Other Liabilities [Member]
Derivatives, Fair Value [Line Items]
Fair value of derivative liability	$ 200	$ 200

Aggregate notional amount specified by the derivative(s). Expressed as an absolute value.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Article 12
-Section 13
-Sentence Column B

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Fair value of investments in debt securities classified as held-to-maturity.

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Including the current and noncurrent portions, the carrying value of junior subordinated long-term debt owed to unconsolidated subsidiary trusts as of the balance sheet date. Such debt places a lender in a lien position behind debt having a higher priority of repayment in liquidation of the entity's assets and was initially scheduled to be repaid after one year or beyond the normal operating cycle if longer.

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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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Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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Amount of time deposit liabilities, including certificates of deposit.

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