Loans and Allowance for Loan Losses (Narrative) (Details)	3 Months Ended		9 Months Ended
	Sep. 30, 2022 USD ($) contract	Sep. 30, 2021 USD ($) contract	Sep. 30, 2022 USD ($) contract	Sep. 30, 2021 USD ($) contract	Jun. 30, 2022 USD ($)	Dec. 31, 2021 USD ($)	Jun. 30, 2021 USD ($)	Dec. 31, 2020 USD ($)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Interest income on non-accrual loans outstanding	$ 1,200,000	$ 4,400,000	$ 6,600,000	$ 10,700,000
Interest income, cash basis method	1,300,000	646,000	2,200,000	1,900,000
Total loans	42,571,458,000		42,571,458,000			$ 39,311,958,000
Allowance for loan losses	421,359,000	492,243,000	421,359,000	492,243,000	$ 407,837,000	427,597,000	$ 516,708,000	$ 605,736,000
Reserve for unfunded commitments	57,900,000		57,900,000			41,900,000
All financing receivable, allowance for credit loss	$ 479,300,000		479,300,000			$ 469,500,000
Allowance for credit loss, increase (decrease)			$ 9,800,000
ACL to loans ratio	1.13%		1.13%
Decrease in ACL to loans ratio			0.0006
Allowance for credit loss, reasonable and supportable forecast period			2 years
Allowance for credit loss, straight-line basis historical period			1 year
Downside bias	70.00%		70.00%			43.00%
Provision for (reversal of) credit losses	$ 25,581,000	(7,868,000)	$ 49,669,000	(51,041,000)
Net chargeoff amount	4,700,000		39,900,000
Financing receivable, allowance for credit loss, period increase (decrease) from increase in size of loan profile	3,000,000		10,500,000
Financing receivable, purchase	152,900,000		514,500,000
Recorded investment	14,932,000	$ 15,229,000	93,857,000	$ 37,504,000
Commitments to land additional funds to TDRs	$ 0		$ 0			$ 0
Troubled Debt Restructuring That Subsequently Defaults
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of contracts | contract	1	2	4	7
Recorded investment	$ 109,000	$ 536,000	$ 539,000	$ 708,000
Baseline
Accounts, Notes, Loans and Financing Receivable [Line Items]
Projected unemployment rate	4.50%		4.50%			5.10%
Average GDP	1.40%		1.40%			2.20%
Substandard
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retail loan substandard period (in days)			90 days
Loss
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retail loan charge off (in days)			120 days
Total commercial and industrial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	$ 21,212,516,000		$ 21,212,516,000			$ 19,622,924,000
Recorded investment	10,332,000	$ 9,036,000	69,964,000	$ 20,583,000
Total commercial and industrial | Small Business Administration (SBA), CARES Act, Paycheck Protection Program
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	42,800,000		42,800,000
Asset Pledged as Collateral
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	$ 14,820,000,000		$ 14,820,000,000			$ 14,190,000,000