Loans and Allowances for Credit Losses Loans and Allowances for Credit Losses, Nonaccrual (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Financing Receivable, Nonaccrual [Line Items]
Nonaccrual	$ 163,172	$ 180,951
Financing Receivable, Nonaccrual, No Allowance	105,712
Financing Receivable, Nonaccrual, With Allowance	57,460
Financing Receivable, Nonaccrual, Related Allowance	9,884
Commercial [Member]
Financing Receivable, Nonaccrual [Line Items]
Nonaccrual	118,624	115,416
Financing Receivable, Nonaccrual, No Allowance	61,164
Financing Receivable, Nonaccrual, With Allowance	57,460
Financing Receivable, Nonaccrual, Related Allowance	9,884
Commercial [Member] \| Energy [Member]
Financing Receivable, Nonaccrual [Line Items]
Nonaccrual	96,448	91,722
Financing Receivable, Nonaccrual, No Allowance	40,424
Financing Receivable, Nonaccrual, With Allowance	56,024
Financing Receivable, Nonaccrual, Related Allowance	9,375
Commercial [Member] \| Healthcare [Member]
Financing Receivable, Nonaccrual [Line Items]
Nonaccrual	4,070	4,480
Financing Receivable, Nonaccrual, No Allowance	4,070
Financing Receivable, Nonaccrual, With Allowance	0
Financing Receivable, Nonaccrual, Related Allowance	0
Commercial [Member] \| Services [Member]
Financing Receivable, Nonaccrual [Line Items]
Nonaccrual	8,425	7,483
Financing Receivable, Nonaccrual, No Allowance	7,258
Financing Receivable, Nonaccrual, With Allowance	1,167
Financing Receivable, Nonaccrual, Related Allowance	240
Commercial [Member] \| General business [Member]
Financing Receivable, Nonaccrual [Line Items]
Nonaccrual	9,681
Financing Receivable, Nonaccrual, No Allowance	9,412
Financing Receivable, Nonaccrual, With Allowance	269
Financing Receivable, Nonaccrual, Related Allowance	269
Commercial real estate [Member]
Financing Receivable, Nonaccrual [Line Items]
Nonaccrual	8,545	27,626
Financing Receivable, Nonaccrual, No Allowance	8,545
Financing Receivable, Nonaccrual, With Allowance	0
Financing Receivable, Nonaccrual, Related Allowance	0
Loans to individuals [Member]
Financing Receivable, Nonaccrual [Line Items]
Nonaccrual	36,003	37,622
Financing Receivable, Nonaccrual, No Allowance	36,003
Financing Receivable, Nonaccrual, With Allowance	0
Financing Receivable, Nonaccrual, Related Allowance	0
Loans to individuals [Member] \| Residential mortgage [Member]
Financing Receivable, Nonaccrual [Line Items]
Nonaccrual	30,721
Financing Receivable, Nonaccrual, No Allowance	30,721
Financing Receivable, Nonaccrual, With Allowance	0
Financing Receivable, Nonaccrual, Related Allowance	0
Loans to individuals [Member] \| Personal [Member]
Financing Receivable, Nonaccrual [Line Items]
Nonaccrual	277	$ 287
Financing Receivable, Nonaccrual, No Allowance	277
Financing Receivable, Nonaccrual, With Allowance	0
Financing Receivable, Nonaccrual, Related Allowance	0
US Government Agency Insured Loans [Member] \| Loans to individuals [Member] \| Residential mortgage [Member]
Financing Receivable, Nonaccrual [Line Items]
Nonaccrual	5,005
Financing Receivable, Nonaccrual, No Allowance	5,005
Financing Receivable, Nonaccrual, With Allowance	0
Financing Receivable, Nonaccrual, Related Allowance	$ 0

Amount of financing receivable on nonaccrual status with a related allowance.

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- Definition

Amount of financing receivable on nonaccrual status with an allowance.

+ References

No definition available.

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- Definition

Amount of financing receivable on nonaccrual status with no allowance for credit loss.

+ 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 (d)
-URI http://asc.fasb.org/extlink&oid=119407570&loc=SL82919258-210447

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+ References

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Amount of financing receivable on nonaccrual status.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 7
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=118936363&loc=d3e5111-111524

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
-Section 50
-Paragraph 16
-Subparagraph (a)
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