Loans Loans - Non-Accrual Loans, Segregated by Class of Loans and Year of Origination (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Loans and Leases Receivable Disclosure [Line Items]
Non-accrual loans	$ 91,578	$ 102,303
Nonperforming Financial Instruments [Member]
Loans and Leases Receivable Disclosure [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	35,572
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	16,778
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	4,680
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	2,846
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	1,300
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	4,023
Financing Receivable, Revolving	17,326
Financing Receivable, Revolving, Converted to Term Loan	9,053
Commercial Portfolio Segment [Member]
Loans and Leases Receivable Disclosure [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	1,189,149
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	669,507
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	399,543
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	285,092
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	133,505
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	131,886
Financing Receivable, Revolving	1,946,379
Non-accrual loans	21,566	26,038
Commercial Portfolio Segment [Member] | Nonperforming Financial Instruments [Member]
Loans and Leases Receivable Disclosure [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	9,317
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	3,743
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	1,886
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	1,263
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	110
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	51
Financing Receivable, Revolving	1,879
Financing Receivable, Revolving, Converted to Term Loan	3,317
Commercial and Industrial Total Energy Loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	667,227
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	57,989
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	21,091
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	7,942
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	2,388
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	5,775
Financing Receivable, Revolving	553,059
Non-accrual loans	54,041	65,761
Commercial and Industrial Total Energy Loans [Member] | Nonperforming Financial Instruments [Member]
Loans and Leases Receivable Disclosure [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	24,149
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	7,021
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	2,204
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	0
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	0
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	0
Financing Receivable, Revolving	15,054
Financing Receivable, Revolving, Converted to Term Loan	5,613
Paycheck Protection Program [Member]
Loans and Leases Receivable Disclosure [Line Items]
Non-accrual loans	0	0
Paycheck Protection Program [Member] | Nonperforming Financial Instruments [Member]
Loans and Leases Receivable Disclosure [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	0
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	0
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	0
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	0
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	0
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	0
Financing Receivable, Revolving	0
Financing Receivable, Revolving, Converted to Term Loan	0
Commercial Real Estate Buildings Land And Other Loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	1,204,132
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	1,142,733
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	940,137
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	810,297
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	553,477
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	950,369
Financing Receivable, Revolving	74,384
Non-accrual loans	13,525	8,912
Commercial Real Estate Buildings Land And Other Loans [Member] | Nonperforming Financial Instruments [Member]
Loans and Leases Receivable Disclosure [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	1,426
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	6,014
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	169
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	1,372
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	840
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	3,590
Financing Receivable, Revolving	114
Financing Receivable, Revolving, Converted to Term Loan	0
Construction Loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	310,240
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	488,536
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	251,868
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	40,441
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	1,164
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	2,731
Financing Receivable, Revolving	179,100
Non-accrual loans	680	665
Construction Loans [Member] | Nonperforming Financial Instruments [Member]
Loans and Leases Receivable Disclosure [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	680
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	0
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	0
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	0
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	0
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	0
Financing Receivable, Revolving	0
Financing Receivable, Revolving, Converted to Term Loan	0
Total consumer real estate loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Non-accrual loans	1,748	922
Total consumer real estate loans [Member] | Nonperforming Financial Instruments [Member]
Loans and Leases Receivable Disclosure [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	0
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	0
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	421
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	211
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	350
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	382
Financing Receivable, Revolving	261
Financing Receivable, Revolving, Converted to Term Loan	123
Consumer Loan [Member]
Loans and Leases Receivable Disclosure [Line Items]
Non-accrual loans	18	$ 5
Consumer Loan [Member] | Nonperforming Financial Instruments [Member]
Loans and Leases Receivable Disclosure [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	0
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	0
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	0
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	0
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	0
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	0
Financing Receivable, Revolving	18
Financing Receivable, Revolving, Converted to Term Loan	0
Revolving Loans Converted to Term [Member] | Commercial Portfolio Segment [Member]
Loans and Leases Receivable Disclosure [Line Items]
Financing Receivable, Revolving, Converted to Term Loan	64,957
Revolving Loans Converted to Term [Member] | Commercial and Industrial Total Energy Loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Financing Receivable, Revolving, Converted to Term Loan	47,897
Revolving Loans Converted to Term [Member] | Commercial Real Estate Buildings Land And Other Loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Financing Receivable, Revolving, Converted to Term Loan	57,609
Revolving Loans Converted to Term [Member] | Construction Loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Financing Receivable, Revolving, Converted to Term Loan	$ 0