Loans Loans - Non-Accrual Loans, Segregated by Class of Loans and Year of Origination (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Loans and Leases Receivable Disclosure [Line Items]
Non-accrual loans	$ 66,727	$ 102,303
Commercial Portfolio Segment [Member]
Loans and Leases Receivable Disclosure [Line Items]
Non-accrual loans	23,913	26,038
Commercial and Industrial Total Energy Loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Non-accrual loans	28,702	65,761
Commercial Real Estate Buildings Land And Other Loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Non-accrual loans	8,224	8,912
Construction Loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Non-accrual loans	3,774	665
Total consumer real estate loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Non-accrual loans	2,094	922
Consumer Loan [Member]
Loans and Leases Receivable Disclosure [Line Items]
Non-accrual loans	20	$ 5
Revolving Credit Facility [Member]
Loans and Leases Receivable Disclosure [Line Items]
Non-accrual loans	9,067
Revolving Credit Facility [Member] | Commercial Portfolio Segment [Member]
Loans and Leases Receivable Disclosure [Line Items]
Non-accrual loans	4,601
Revolving Credit Facility [Member] | Commercial and Industrial Total Energy Loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Non-accrual loans	3,035
Revolving Credit Facility [Member] | Commercial Real Estate Buildings Land And Other Loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Non-accrual loans	568
Revolving Credit Facility [Member] | Construction Loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Non-accrual loans	0
Revolving Credit Facility [Member] | Total consumer real estate loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Non-accrual loans	844
Revolving Credit Facility [Member] | Consumer Loan [Member]
Loans and Leases Receivable Disclosure [Line Items]
Non-accrual loans	19
Revolving Loans Converted to Term [Member]
Loans and Leases Receivable Disclosure [Line Items]
Non-accrual loans	29,863
Revolving Loans Converted to Term [Member] | Commercial Portfolio Segment [Member]
Loans and Leases Receivable Disclosure [Line Items]
Non-accrual loans	4,135
Revolving Loans Converted to Term [Member] | Commercial and Industrial Total Energy Loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Non-accrual loans	25,667
Revolving Loans Converted to Term [Member] | Commercial Real Estate Buildings Land And Other Loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Non-accrual loans	0
Revolving Loans Converted to Term [Member] | Construction Loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Non-accrual loans	0
Revolving Loans Converted to Term [Member] | Total consumer real estate loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Non-accrual loans	61
Revolving Loans Converted to Term [Member] | Consumer Loan [Member]
Loans and Leases Receivable Disclosure [Line Items]
Non-accrual loans	0
2020 [Member]
Loans and Leases Receivable Disclosure [Line Items]
Non-accrual loans	0
2020 [Member] | Commercial Portfolio Segment [Member]
Loans and Leases Receivable Disclosure [Line Items]
Non-accrual loans	0
2020 [Member] | Commercial and Industrial Total Energy Loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Non-accrual loans	0
2020 [Member] | Commercial Real Estate Buildings Land And Other Loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Non-accrual loans	0
2020 [Member] | Construction Loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Non-accrual loans	0
2020 [Member] | Total consumer real estate loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Non-accrual loans	0
2020 [Member] | Consumer Loan [Member]
Loans and Leases Receivable Disclosure [Line Items]
Non-accrual loans	0
2019 [Member]
Loans and Leases Receivable Disclosure [Line Items]
Non-accrual loans	9,169
2019 [Member] | Commercial Portfolio Segment [Member]
Loans and Leases Receivable Disclosure [Line Items]
Non-accrual loans	3,187
2019 [Member] | Commercial and Industrial Total Energy Loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Non-accrual loans	0
2019 [Member] | Commercial Real Estate Buildings Land And Other Loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Non-accrual loans	2,207
2019 [Member] | Construction Loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Non-accrual loans	3,774
2019 [Member] | Total consumer real estate loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Non-accrual loans	0
2019 [Member] | Consumer Loan [Member]
Loans and Leases Receivable Disclosure [Line Items]
Non-accrual loans	1
2018 [Member]
Loans and Leases Receivable Disclosure [Line Items]
Non-accrual loans	9,046
2018 [Member] | Commercial Portfolio Segment [Member]
Loans and Leases Receivable Disclosure [Line Items]
Non-accrual loans	9,012
2018 [Member] | Commercial and Industrial Total Energy Loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Non-accrual loans	0
2018 [Member] | Commercial Real Estate Buildings Land And Other Loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Non-accrual loans	34
2018 [Member] | Construction Loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Non-accrual loans	0
2018 [Member] | Total consumer real estate loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Non-accrual loans	0
2018 [Member] | Consumer Loan [Member]
Loans and Leases Receivable Disclosure [Line Items]
Non-accrual loans	0
2017 [Member]
Loans and Leases Receivable Disclosure [Line Items]
Non-accrual loans	4,129
2017 [Member] | Commercial Portfolio Segment [Member]
Loans and Leases Receivable Disclosure [Line Items]
Non-accrual loans	2,448
2017 [Member] | Commercial and Industrial Total Energy Loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Non-accrual loans	0
2017 [Member] | Commercial Real Estate Buildings Land And Other Loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Non-accrual loans	1,470
2017 [Member] | Construction Loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Non-accrual loans	0
2017 [Member] | Total consumer real estate loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Non-accrual loans	211
2017 [Member] | Consumer Loan [Member]
Loans and Leases Receivable Disclosure [Line Items]
Non-accrual loans	0
2016 [Member]
Loans and Leases Receivable Disclosure [Line Items]
Non-accrual loans	1,040
2016 [Member] | Commercial Portfolio Segment [Member]
Loans and Leases Receivable Disclosure [Line Items]
Non-accrual loans	384
2016 [Member] | Commercial and Industrial Total Energy Loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Non-accrual loans	0
2016 [Member] | Commercial Real Estate Buildings Land And Other Loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Non-accrual loans	306
2016 [Member] | Construction Loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Non-accrual loans	0
2016 [Member] | Total consumer real estate loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Non-accrual loans	350
2016 [Member] | Consumer Loan [Member]
Loans and Leases Receivable Disclosure [Line Items]
Non-accrual loans	0
Prior Years [Member]
Loans and Leases Receivable Disclosure [Line Items]
Non-accrual loans	4,413
Prior Years [Member] | Commercial Portfolio Segment [Member]
Loans and Leases Receivable Disclosure [Line Items]
Non-accrual loans	146
Prior Years [Member] | Commercial and Industrial Total Energy Loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Non-accrual loans	0
Prior Years [Member] | Commercial Real Estate Buildings Land And Other Loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Non-accrual loans	3,639
Prior Years [Member] | Construction Loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Non-accrual loans	0
Prior Years [Member] | Total consumer real estate loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Non-accrual loans	628
Prior Years [Member] | Consumer Loan [Member]
Loans and Leases Receivable Disclosure [Line Items]
Non-accrual loans	$ 0