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Amount excluding accrued interest, of allowance for credit loss on financing receivable.

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Amount, before troubled debt restructuring, of financing receivable to be modified.

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Allowance for Credit Losses (Allowance for Credit Losses Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Jun. 30, 2021	Dec. 31, 2020	Jun. 30, 2020	Jan. 01, 2020	Dec. 31, 2019
Financing Receivable, Allowance for Credit Loss [Line Items]
Nonaccrual loans with no related allowance for credit losses	$ 47,300		$ 47,300
Loans reasonably expected to be modified into TDRs			335
Allowance for loan losses	296,055	$ 388,908	296,055	$ 388,908	$ 304,031	$ 379,910	$ 373,109		$ 158,461
Provision for (reversal of) credit losses	(7,909)	25,028	(68,584)	213,051
Loan net charge-offs	2		15,300
Held-to-maturity securities, allowance for credit loss	83	63	83	63		59
Provision for credit losses	(7)		22
Cumulative effect, period of adoption, adjustment
Financing Receivable, Allowance for Credit Loss [Line Items]
Allowance for loan losses								$ 47,300	$ 47,344
Held-to-maturity securities, allowance for credit loss								74
Loans acquired with deteriorated credit quality \| Cumulative effect, period of adoption, adjustment
Financing Receivable, Allowance for Credit Loss [Line Items]
Allowance for loan losses								11,000
Loans acquired without deteriorated credit quality \| Cumulative effect, period of adoption, adjustment
Financing Receivable, Allowance for Credit Loss [Line Items]
Allowance for loan losses								3,200
Unfunded lending-related commitments
Financing Receivable, Allowance for Credit Loss [Line Items]
Allowance for loan losses	47,443	62,949	47,443	62,949		60,536
Unfunded lending-related commitments \| Cumulative effect, period of adoption, adjustment
Financing Receivable, Allowance for Credit Loss [Line Items]
Allowance for loan losses								33,200
Loans
Financing Receivable, Allowance for Credit Loss [Line Items]
Allowance for loan losses	$ 248,612	$ 325,959	$ 248,612	$ 325,959		$ 319,374
Loans \| Cumulative effect, period of adoption, adjustment
Financing Receivable, Allowance for Credit Loss [Line Items]
Allowance for loan losses								$ 14,200