Loans Loans - Allowance for Credit Loss By Loan Class Calculated in Accordance With CECL Methodology (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans and Leases Receivable, Allowance	$ 250,061	$ 132,167
Commercial Portfolio Segment [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans and Leases Receivable, Allowance	98,536	51,593
Commercial and Industrial Total Energy Loans [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans and Leases Receivable, Allowance	40,817	37,382
Commercial Real Estate Portfolio Segment [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans and Leases Receivable, Allowance	93,425	31,037
Total consumer real estate loans [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans and Leases Receivable, Allowance	8,998	4,113
Consumer Loan [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans and Leases Receivable, Allowance	8,285	8,042
Modeled Expected Credit Losses [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans and Leases Receivable, Allowance	243,060
Modeled Expected Credit Losses [Member] | Commercial Portfolio Segment [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans and Leases Receivable, Allowance	86,016
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	17,977
Modeled Expected Credit Losses [Member] | Commercial Real Estate Portfolio Segment [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans and Leases Receivable, Allowance	121,978
Modeled Expected Credit Losses [Member] | Total consumer real estate loans [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans and Leases Receivable, Allowance	8,865
Modeled Expected Credit Losses [Member] | Consumer Loan [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans and Leases Receivable, Allowance	8,224
Q-factor adjustments [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans and Leases Receivable, Allowance	(8,671)
Q-factor adjustments [Member] | Commercial Portfolio Segment [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans and Leases Receivable, Allowance	430
Q-factor adjustments [Member] | Commercial and Industrial Total Energy Loans [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans and Leases Receivable, Allowance	20,590
Q-factor adjustments [Member] | Commercial Real Estate Portfolio Segment [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans and Leases Receivable, Allowance	(29,867)
Q-factor adjustments [Member] | Total consumer real estate loans [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans and Leases Receivable, Allowance	133
Q-factor adjustments [Member] | Consumer Loan [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans and Leases Receivable, Allowance	43
Specific Valuation Allowances [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans and Leases Receivable, Allowance	15,672	28,483
Specific Valuation Allowances [Member] | Commercial Portfolio Segment [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans and Leases Receivable, Allowance	12,090	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	2,250	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	1,314	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