Loans Loans - Allowance for Credit Loss By Loan Class Calculated in Accordance With CECL Methodology (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans and Leases Receivable, Allowance		$ 132,167
Commercial Portfolio Segment [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans and Leases Receivable, Allowance		51,593
Commercial and Industrial Total Energy Loans [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans and Leases Receivable, Allowance		37,382
Commercial Real Estate Portfolio Segment [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans and Leases Receivable, Allowance		31,037
Total consumer real estate loans [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans and Leases Receivable, Allowance		4,113
Consumer Loan [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans and Leases Receivable, Allowance		8,042
Modeled Expected Credit Losses [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans and Leases Receivable, Allowance	$ 234,151
Modeled Expected Credit Losses [Member] | Commercial Portfolio Segment [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans and Leases Receivable, Allowance	68,896
Modeled Expected Credit Losses [Member] | Commercial and Industrial Total Energy Loans [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans and Leases Receivable, Allowance	21,644
Modeled Expected Credit Losses [Member] | Commercial Real Estate Portfolio Segment [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans and Leases Receivable, Allowance	125,965
Modeled Expected Credit Losses [Member] | Total consumer real estate loans [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans and Leases Receivable, Allowance	10,226
Modeled Expected Credit Losses [Member] | Consumer Loan [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans and Leases Receivable, Allowance	7,420
Q-factor adjustments [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans and Leases Receivable, Allowance	14,380
Q-factor adjustments [Member] | Commercial Portfolio Segment [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans and Leases Receivable, Allowance	(1,647)
Q-factor adjustments [Member] | Commercial and Industrial Total Energy Loans [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans and Leases Receivable, Allowance	24,630
Q-factor adjustments [Member] | Commercial Real Estate Portfolio Segment [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans and Leases Receivable, Allowance	(8,685)
Q-factor adjustments [Member] | Total consumer real estate loans [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans and Leases Receivable, Allowance	51
Q-factor adjustments [Member] | Consumer Loan [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans and Leases Receivable, Allowance	31
Specific Valuation Allowances [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans and Leases Receivable, Allowance	14,944	28,483
Specific Valuation Allowances [Member] | Commercial Portfolio Segment [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans and Leases Receivable, Allowance	5,256	7,849
Specific Valuation Allowances [Member] | Commercial and Industrial Total Energy Loans [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans and Leases Receivable, Allowance	8,357	20,246
Specific Valuation Allowances [Member] | Commercial Real Estate Portfolio Segment [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans and Leases Receivable, Allowance	1,313	383
Specific Valuation Allowances [Member] | Total consumer real estate loans [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans and Leases Receivable, Allowance	0	0
Specific Valuation Allowances [Member] | Consumer Loan [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans and Leases Receivable, Allowance	$ 18	$ 5