Loans and Allowance for Credit Losses, Loans by Portfolio Type (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Loan receivables disclosure [Abstract]
Loans, fixed rate of interest	$ 8,365,827	$ 6,134,362
Loans, variable rate of interest	15,534,667	15,435,674
Loans, non-accrual	255,396	180,951
Total	24,155,890	21,750,987
Past Due 90 Days or More and Accruing	232,193	7,680
Credit Commitments [Abstract]
Outstanding commitments to extend credit	10,300,000
Outstanding standby letters of credit	693,000
Commercial [Member]
Loan receivables disclosure [Abstract]
Loans, fixed rate of interest	3,215,865	3,231,485
Loans, variable rate of interest	10,740,646	10,684,749
Loans, non-accrual	201,999	115,416
Total	14,158,510	14,031,650
Past Due 90 Days or More and Accruing	10,465
Commercial real estate [Member]
Loan receivables disclosure [Abstract]
Loans, fixed rate of interest	1,029,544	1,056,321
Loans, variable rate of interest	3,510,644	3,349,836
Loans, non-accrual	13,956	27,626
Total	4,554,144	4,433,783
Past Due 90 Days or More and Accruing	469
Paycheck Protection Program
Loan receivables disclosure [Abstract]
Loans, fixed rate of interest	2,081,428
Loans, variable rate of interest	0
Loans, non-accrual	0
Total	2,081,428
Past Due 90 Days or More and Accruing	0
Loans to individuals [Member]
Loan receivables disclosure [Abstract]
Loans, fixed rate of interest	2,038,990
Loans, variable rate of interest	1,283,377
Loans, non-accrual	39,441
Total	3,361,808	2,084,172
Past Due 90 Days or More and Accruing	221,259
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	1,813,442	2,084,172
Past Due 90 Days or More and Accruing	42
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	1,226,097	$ 1,201,382
Past Due 90 Days or More and Accruing	$ 16

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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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-Topic 310
-SubTopic 10
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-Publisher FASB
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- Definition

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

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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
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-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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-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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