Loans Loans - Allowance for Credit Loss By Loan Class Calculated in Accordance With CECL Methodology (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans and Leases Receivable, Allowance	$ 263,881	$ 132,167
Commercial Portfolio Segment [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans and Leases Receivable, Allowance	92,152	51,593
Commercial and Industrial Total Energy Loans [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans and Leases Receivable, Allowance	103,201	37,382
Commercial Real Estate Portfolio Segment [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans and Leases Receivable, Allowance	52,319	31,037
Total consumer real estate loans [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans and Leases Receivable, Allowance	8,170	4,113
Consumer Loan [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans and Leases Receivable, Allowance	8,039	8,042
Modeled Expected Credit Losses [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans and Leases Receivable, Allowance	133,736
Modeled Expected Credit Losses [Member] | Commercial Portfolio Segment [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans and Leases Receivable, Allowance	69,446
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	15,425
Modeled Expected Credit Losses [Member] | Commercial Real Estate Portfolio Segment [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans and Leases Receivable, Allowance	34,941
Modeled Expected Credit Losses [Member] | Total consumer real estate loans [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans and Leases Receivable, Allowance	6,974
Modeled Expected Credit Losses [Member] | Consumer Loan [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans and Leases Receivable, Allowance	6,950
Q-factor adjustments [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans and Leases Receivable, Allowance	117,517
Q-factor adjustments [Member] | Commercial Portfolio Segment [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans and Leases Receivable, Allowance	13,501
Q-factor adjustments [Member] | Commercial and Industrial Total Energy Loans [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans and Leases Receivable, Allowance	87,776
Q-factor adjustments [Member] | Commercial Real Estate Portfolio Segment [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans and Leases Receivable, Allowance	13,974
Q-factor adjustments [Member] | Total consumer real estate loans [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans and Leases Receivable, Allowance	1,196
Q-factor adjustments [Member] | Consumer Loan [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans and Leases Receivable, Allowance	1,070
Specific Valuation Allowances [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans and Leases Receivable, Allowance	12,628	28,483
Specific Valuation Allowances [Member] | Commercial Portfolio Segment [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans and Leases Receivable, Allowance	9,205	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	0	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	3,404	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	$ 19	$ 5