Loans and Allowance for Credit Losses, Loans by Portfolio Type (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Loan receivables disclosure [Abstract]
Loans, fixed rate of interest	$ 6,667,276	$ 6,134,362
Loans, variable rate of interest	16,914,871	15,435,674
Loans, non-accrual	221,153	180,951
Total	23,803,300	21,750,987
Past Due 90 Days or More and Accruing	124,872	7,680
Credit Commitments [Abstract]
Outstanding commitments to extend credit	10,400,000
Outstanding standby letters of credit	678,000
Commercial [Member]
Loan receivables disclosure [Abstract]
Loans, fixed rate of interest	1,424,416	3,231,485
Loans, variable rate of interest	11,971,337	10,684,749
Loans, non-accrual	169,953	115,416
Total	13,565,706	14,031,650
Past Due 90 Days or More and Accruing	672
Commercial real estate [Member]
Loan receivables disclosure [Abstract]
Loans, fixed rate of interest	1,012,882	1,056,321
Loans, variable rate of interest	3,667,866	3,349,836
Loans, non-accrual	12,952	27,626
Total	4,693,700	4,433,783
Past Due 90 Days or More and Accruing	4,771
Paycheck Protection Program
Loan receivables disclosure [Abstract]
Loans, fixed rate of interest	2,097,325
Loans, variable rate of interest	0
Loans, non-accrual	0
Total	2,097,325
Past Due 90 Days or More and Accruing	0
Loans to individuals [Member]
Loan receivables disclosure [Abstract]
Loans, fixed rate of interest	2,132,653
Loans, variable rate of interest	1,275,668
Loans, non-accrual	38,248
Total	3,446,569	2,084,172
Past Due 90 Days or More and Accruing	119,429
Loans to individuals [Member] \| Residential mortgage [Member]
Loan receivables disclosure [Abstract]
Loans, fixed rate of interest		1,652,653
Loans, variable rate of interest		393,897
Loans, non-accrual		37,622
Total	1,849,144	2,084,172
Past Due 90 Days or More and Accruing	2,241
Loans to individuals [Member] \| Personal [Member]
Loan receivables disclosure [Abstract]
Loans, fixed rate of interest		193,903
Loans, variable rate of interest		1,007,192
Loans, non-accrual		287
Total	1,213,178	$ 1,201,382
Past Due 90 Days or More and Accruing	$ 0

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- Definition

Amount of financing receivable 90 days or more past due and still accruing.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
-Section 50
-Paragraph 16
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=121599337&loc=SL82919258-210447

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
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-Publisher FASB
-Name Accounting Standards Codification
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- Definition

The total amount of the contingent obligation under letters of credit outstanding as of the reporting date.

+ References

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Amount before allowance of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Includes deferred interest and fees, undisbursed portion of loan balance, unamortized costs and premiums and discounts from face amounts. Excludes loans and leases covered under loss sharing agreements.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 45
-Paragraph 2
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- Definition

Reflects the carrying amount of loans deemed to be questionable as to collection on which no interest is continuing to be recognized.

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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
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- Definition

Amount of loan with fixed rate of interest.

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Amount of loan with variable or adjustable rate of interest.

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- Definition

Unused amount of commitments to extend credit to customers.

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