Loans and Allowances for Credit Losses Loans and Allowances for Credit Losses, Nonaccrual (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Financing Receivable, Nonaccrual [Line Items]
Nonaccrual	$ 141,947	$ 234,693
Financing Receivable, Nonaccrual, No Allowance	118,574	167,878
Financing Receivable, Nonaccrual, With Allowance	23,373	66,815
Financing Receivable, Nonaccrual, Related Allowance	10,184	22,441
Commercial [Member]
Financing Receivable, Nonaccrual [Line Items]
Nonaccrual	80,674	167,159
Financing Receivable, Nonaccrual, No Allowance	65,545	113,945
Financing Receivable, Nonaccrual, With Allowance	15,129	53,214
Financing Receivable, Nonaccrual, Related Allowance	7,835	19,052
Commercial [Member] | Energy [Member]
Financing Receivable, Nonaccrual [Line Items]
Nonaccrual	45,500	125,059
Financing Receivable, Nonaccrual, No Allowance	40,998	76,633
Financing Receivable, Nonaccrual, With Allowance	4,502	48,426
Financing Receivable, Nonaccrual, Related Allowance	2,417	16,478
Commercial [Member] | Healthcare [Member]
Financing Receivable, Nonaccrual [Line Items]
Nonaccrual	509	3,645
Financing Receivable, Nonaccrual, No Allowance	509	3,645
Financing Receivable, Nonaccrual, With Allowance	0	0
Financing Receivable, Nonaccrual, Related Allowance	0	0
Commercial [Member] | Services [Member]
Financing Receivable, Nonaccrual [Line Items]
Nonaccrual	25,714	25,598
Financing Receivable, Nonaccrual, No Allowance	18,512	20,810
Financing Receivable, Nonaccrual, With Allowance	7,202	4,788
Financing Receivable, Nonaccrual, Related Allowance	4,918	2,574
Commercial [Member] | General business [Member]
Financing Receivable, Nonaccrual [Line Items]
Nonaccrual	8,951	12,857
Financing Receivable, Nonaccrual, No Allowance	5,526	12,857
Financing Receivable, Nonaccrual, With Allowance	3,425	0
Financing Receivable, Nonaccrual, Related Allowance	500	0
Commercial real estate [Member]
Financing Receivable, Nonaccrual [Line Items]
Nonaccrual	21,223	27,246
Financing Receivable, Nonaccrual, No Allowance	12,979	13,645
Financing Receivable, Nonaccrual, With Allowance	8,244	13,601
Financing Receivable, Nonaccrual, Related Allowance	2,349	3,389
Loans to individuals [Member]
Financing Receivable, Nonaccrual [Line Items]
Nonaccrual	40,050	40,288
Financing Receivable, Nonaccrual, No Allowance	40,050	40,288
Financing Receivable, Nonaccrual, With Allowance	0	0
Financing Receivable, Nonaccrual, Related Allowance	0	0
Loans to individuals [Member] | Residential mortgage [Member]
Financing Receivable, Nonaccrual [Line Items]
Nonaccrual	30,674	32,228
Financing Receivable, Nonaccrual, No Allowance	30,674	32,228
Financing Receivable, Nonaccrual, With Allowance	0	0
Financing Receivable, Nonaccrual, Related Allowance	0	0
Loans to individuals [Member] | Personal [Member]
Financing Receivable, Nonaccrual [Line Items]
Nonaccrual	188	319
Financing Receivable, Nonaccrual, No Allowance	188	319
Financing Receivable, Nonaccrual, With Allowance	0	0
Financing Receivable, Nonaccrual, Related Allowance	0	0
US Government Agency Insured Loans [Member] | Loans to individuals [Member] | Residential mortgage [Member]
Financing Receivable, Nonaccrual [Line Items]
Nonaccrual	9,188	7,741
Financing Receivable, Nonaccrual, No Allowance	9,188	7,741
Financing Receivable, Nonaccrual, With Allowance	0	0
Financing Receivable, Nonaccrual, Related Allowance	$ 0	$ 0