Fair Value - Financial Instruments not Required to be Carried at Fair Value and Off-Balance Sheet Commitments (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Lease and lease commitments excluded
Financing leases	$ 171,400	$ 180,000
Financing lease commitments	0	0
Book Value
Financial assets:
Cash and cash equivalents	1,114,365	1,052,058
Loans	11,978,338	11,340,338
Financial liabilities:
Deposits	17,595,483	16,794,532
Short-term borrowings		9,151
Book Value \| Commitments to extend credit
Off-balance sheet financial instruments:
Off-balance sheet financial instrument amount	20,180	20,677
Book Value \| Standby letters of credit
Off-balance sheet financial instruments:
Off-balance sheet financial instrument amount	2,857	876
Book Value \| Commercial Letters of credit
Off-balance sheet financial instruments:
Off-balance sheet financial instrument amount	15	17
Estimated Fair Value
Financial assets:
Cash and cash equivalents	1,114,364	1,052,053
Loans	11,979,164	11,306,675
Financial liabilities:
Deposits	17,590,077	16,786,880
Short-term borrowings		9,109
Estimated Fair Value \| Commitments to extend credit
Off-balance sheet financial instruments:
Off-balance sheet financial instrument amount	20,180	20,677
Estimated Fair Value \| Standby letters of credit
Off-balance sheet financial instruments:
Off-balance sheet financial instrument amount	2,857	876
Estimated Fair Value \| Commercial Letters of credit
Off-balance sheet financial instruments:
Off-balance sheet financial instrument amount	15	17
Estimated Fair Value \| Level 1
Financial assets:
Cash and cash equivalents	321,319	253,827
Financial liabilities:
Deposits	12,950,356	13,055,935
Estimated Fair Value \| Level 2
Financial assets:
Cash and cash equivalents	793,045	798,226
Financial liabilities:
Deposits	4,639,721	3,730,945
Short-term borrowings		9,109
Estimated Fair Value \| Level 3
Financial assets:
Loans	11,979,164	11,306,675
Estimated Fair Value \| Level 3 \| Commitments to extend credit
Off-balance sheet financial instruments:
Off-balance sheet financial instrument amount	20,180	20,677
Estimated Fair Value \| Level 3 \| Standby letters of credit
Off-balance sheet financial instruments:
Off-balance sheet financial instrument amount	2,857	876
Estimated Fair Value \| Level 3 \| Commercial Letters of credit
Off-balance sheet financial instruments:
Off-balance sheet financial instrument amount	$ 15	$ 17

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- Definition

Amount before allowance and after deduction of deferred interest and fees, unamortized costs and premiums and discounts from face amounts, of commercial and consumer financing leases held in portfolio.

+ References

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Unused amount of commitments to extend credit to customers under financing leases.

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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

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Cash Equivalents
-URI http://asc.fasb.org/extlink&oid=6507016

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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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The fair value of financial liabilities, which are not recognized in the financial statements (off-balance sheet) because they fail to meet some other criterion for recognition.

+ 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)
-URI http://asc.fasb.org/extlink&oid=73719730&loc=d3e13433-108611

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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
-Glossary Loan
-URI http://asc.fasb.org/extlink&oid=6517073

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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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