Fair Value Measurements - Carrying Amounts and Fair Value (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Investment securities:
Held-to-maturity	$ 655,959	$ 608,531
Nonrecurring
Deposits:
Impaired loans recorded at fair value on a nonrecurring basis	68,379	63,572
Nonrecurring \| Impaired originated loans
Deposits:
Impaired loans recorded at fair value on a nonrecurring basis	65,565	62,184
Level 3 \| Nonrecurring
Deposits:
Impaired loans recorded at fair value on a nonrecurring basis	68,379	63,572
Level 3 \| Nonrecurring \| Impaired originated loans
Deposits:
Impaired loans recorded at fair value on a nonrecurring basis	65,565	62,184
Carrying Amount \| Level 1
Financial assets:
Cash and cash equivalents	709,211	474,402
Carrying Amount \| Level 2
Investment securities:
Held-to-maturity	656,676	622,927
Nonmarketable equity securities	180,098	97,350
Interest receivable	51,928	42,235
Bank-owned life insurance	146,626	143,718
Deposits:
Deposits without defined maturities	10,691,272	9,862,755
Time deposits	3,113,973	3,010,367
Total deposits	13,805,245	12,873,122
Interest payable	5,210	5,415
Securities sold under agreements to repurchase with customers	414,597	343,047
Short-term borrowings	1,900,000	825,000
Long-term borrowings	397,845	597,847
Carrying Amount \| Level 3
Investment securities:
Held-to-maturity	500	500
Net loans	13,747,608	12,912,511
Fair Value \| Level 1
Financial assets:
Cash and cash equivalents	709,211	474,402
Fair Value \| Level 2
Investment securities:
Held-to-maturity	655,594	608,221
Nonmarketable equity securities	180,098	97,350
Interest receivable	51,928	42,235
Bank-owned life insurance	146,626	143,718
Deposits:
Deposits without defined maturities	10,691,272	9,862,755
Time deposits	3,113,921	3,010,048
Total deposits	13,805,193	12,872,803
Interest payable	5,210	5,415
Securities sold under agreements to repurchase with customers	414,597	343,047
Short-term borrowings	1,899,794	825,000
Long-term borrowings	393,547	591,227
Fair Value \| Level 3
Investment securities:
Held-to-maturity	365	310
Net loans	$ 13,896,015	$ 13,069,315

Fair value portion of deposits without defined maturities.

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- Definition

Fair value portion of interest receivable.

+ References

No definition available.

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- Definition

Investment securities.

+ References

No definition available.

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- Definition

Fair value of nonmarketable equity securities.

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No definition available.

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- Definition

Fair value portion of time deposits.

+ References

No definition available.

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- Definition

Fair value portion of accrued expenses.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.20)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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- Definition

This element represents the aggregate of the assets reported on the balance sheet at period end measured at fair value on a nonrecurring basis by the entity. This element is intended to be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements.

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No definition available.

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- Definition

The carrying amount of a life insurance policy on an officer, executive or employee for which the reporting entity (a bank) is entitled to proceeds from the policy upon death of the insured or surrender of the insurance policy.

+ 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)
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

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- Definition

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

No definition available.

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- Definition

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

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- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 5
-Subparagraph (aa)
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- Definition

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
-URI http://asc.fasb.org/subtopic&trid=2196772

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- Definition

The fair value amount of long-term debt whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission.

+ References

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+ Details

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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.

+ References

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 10
-URI http://asc.fasb.org/extlink&oid=77997519&loc=d3e13433-108611

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- Definition

This element represents the portion of the balance sheet assertion valued at fair value by the entity whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission. This item represents the amount of short-term debt existing as of the balance sheet date.

+ References

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