Loans and Allowance for Credit Losses, Impaired Loans (Details) $ in Thousands	Dec. 31, 2019 USD ($)
Impaired loans [Abstract]
Impaired loans, unpaid principal balance	$ 467,714
Impaired loans, recorded investment, total	372,645
Impaired loans, recorded investment with no related allowance	323,505
Impaired loans, recorded investment with related allowance	49,140
Impaired loans, related allowance	17,414
Commercial [Member]
Impaired loans [Abstract]
Impaired loans, unpaid principal balance	195,193
Impaired loans, recorded investment, total	115,416
Impaired loans, recorded investment with no related allowance	66,276
Impaired loans, recorded investment with related allowance	49,140
Impaired loans, related allowance	17,414
Commercial [Member] | Energy [Member]
Impaired loans [Abstract]
Impaired loans, unpaid principal balance	149,441
Impaired loans, recorded investment, total	91,722
Impaired loans, recorded investment with no related allowance	44,244
Impaired loans, recorded investment with related allowance	47,478
Impaired loans, related allowance	16,854
Commercial [Member] | Services [Member]
Impaired loans [Abstract]
Impaired loans, unpaid principal balance	10,923
Impaired loans, recorded investment, total	7,483
Impaired loans, recorded investment with no related allowance	6,301
Impaired loans, recorded investment with related allowance	1,182
Impaired loans, related allowance	240
Commercial [Member] | Wholesale/retail [Member]
Impaired loans [Abstract]
Impaired loans, unpaid principal balance	1,980
Impaired loans, recorded investment, total	1,163
Impaired loans, recorded investment with no related allowance	902
Impaired loans, recorded investment with related allowance	261
Impaired loans, related allowance	101
Commercial [Member] | Manufacturing [Member]
Impaired loans [Abstract]
Impaired loans, unpaid principal balance	10,848
Impaired loans, recorded investment, total	10,133
Impaired loans, recorded investment with no related allowance	9,914
Impaired loans, recorded investment with related allowance	219
Impaired loans, related allowance	219
Commercial [Member] | Healthcare [Member]
Impaired loans [Abstract]
Impaired loans, unpaid principal balance	13,774
Impaired loans, recorded investment, total	4,480
Impaired loans, recorded investment with no related allowance	4,480
Impaired loans, recorded investment with related allowance	0
Impaired loans, related allowance	0
Commercial [Member] | Public finance [Member]
Impaired loans [Abstract]
Impaired loans, unpaid principal balance	0
Impaired loans, recorded investment, total	0
Impaired loans, recorded investment with no related allowance	0
Impaired loans, recorded investment with related allowance	0
Impaired loans, related allowance	0
Commercial [Member] | Other commercial and industrial [Member]
Impaired loans [Abstract]
Impaired loans, unpaid principal balance	8,227
Impaired loans, recorded investment, total	435
Impaired loans, recorded investment with no related allowance	435
Impaired loans, recorded investment with related allowance	0
Impaired loans, related allowance	0
Commercial real estate [Member]
Impaired loans [Abstract]
Impaired loans, unpaid principal balance	30,139
Impaired loans, recorded investment, total	27,626
Impaired loans, recorded investment with no related allowance	27,626
Impaired loans, recorded investment with related allowance	0
Impaired loans, related allowance	0
Commercial real estate [Member] | Residential construction and land development [Member]
Impaired loans [Abstract]
Impaired loans, unpaid principal balance	1,306
Impaired loans, recorded investment, total	350
Impaired loans, recorded investment with no related allowance	350
Impaired loans, recorded investment with related allowance	0
Impaired loans, related allowance	0
Commercial real estate [Member] | Retail [Member]
Impaired loans [Abstract]
Impaired loans, unpaid principal balance	20,265
Impaired loans, recorded investment, total	18,868
Impaired loans, recorded investment with no related allowance	18,868
Impaired loans, recorded investment with related allowance	0
Impaired loans, related allowance	0
Commercial real estate [Member] | Office [Member]
Impaired loans [Abstract]
Impaired loans, unpaid principal balance	0
Impaired loans, recorded investment, total	0
Impaired loans, recorded investment with no related allowance	0
Impaired loans, recorded investment with related allowance	0
Impaired loans, related allowance	0
Commercial real estate [Member] | Multifamily [Member]
Impaired loans [Abstract]
Impaired loans, unpaid principal balance	6,858
Impaired loans, recorded investment, total	6,858
Impaired loans, recorded investment with no related allowance	6,858
Impaired loans, recorded investment with related allowance	0
Impaired loans, related allowance	0
Commercial real estate [Member] | Industrial [Member]
Impaired loans [Abstract]
Impaired loans, unpaid principal balance	909
Impaired loans, recorded investment, total	909
Impaired loans, recorded investment with no related allowance	909
Impaired loans, recorded investment with related allowance	0
Impaired loans, related allowance	0
Commercial real estate [Member] | Other commercial real estate [Member]
Impaired loans [Abstract]
Impaired loans, unpaid principal balance	801
Impaired loans, recorded investment, total	641
Impaired loans, recorded investment with no related allowance	641
Impaired loans, recorded investment with related allowance	0
Impaired loans, related allowance	0
Loans to individuals [Member] | Permanent Residential Mortgage [Member]
Impaired loans [Abstract]
Impaired loans, unpaid principal balance	24,868
Impaired loans, recorded investment, total	20,441
Impaired loans, recorded investment with no related allowance	20,441
Impaired loans, recorded investment with related allowance	0
Impaired loans, related allowance	0
Loans to individuals [Member] | Permanent Residential Mortgage [Member] | US Government Agency Insured Loans [Member]
Impaired loans [Abstract]
Impaired loans, unpaid principal balance	204,187
Impaired loans, recorded investment, total	197,794
Impaired loans, recorded investment with no related allowance	197,794
Impaired loans, recorded investment with related allowance	0
Impaired loans, related allowance	0
Loans to individuals [Member] | Home equity [Member]
Impaired loans [Abstract]
Impaired loans, unpaid principal balance	12,967
Impaired loans, recorded investment, total	11,081
Impaired loans, recorded investment with no related allowance	11,081
Impaired loans, recorded investment with related allowance	0
Impaired loans, related allowance	0
Loans to individuals [Member] | Residential mortgage [Member]
Impaired loans [Abstract]
Impaired loans, unpaid principal balance	242,022
Impaired loans, recorded investment, total	229,316
Impaired loans, recorded investment with no related allowance	229,316
Impaired loans, recorded investment with related allowance	0
Impaired loans, related allowance	0
Loans to individuals [Member] | Personal [Member]
Impaired loans [Abstract]
Impaired loans, unpaid principal balance	360
Impaired loans, recorded investment, total	287
Impaired loans, recorded investment with no related allowance	287
Impaired loans, recorded investment with related allowance	0
Impaired loans, related allowance	$ 0