Income Taxes [Line Items]

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- Definition

Unrecognized Tax Benefits Including Income Tax Penalties And Interest Accrued

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- Definition

Unrecognized tax benefits, interest on income taxes expense benefit.

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- Definition

Amount before allocation of valuation allowances of deferred tax asset attributable to deductible capital loss carryforwards.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 6
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482685/740-10-50-6

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- Definition

Amount after allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences and carryforwards.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482685/740-10-50-2

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- Definition

Amount of deferred tax assets for which it is more likely than not that a tax benefit will not be realized.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482685/740-10-50-2

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- Definition

Amount of deferred tax liability not recognized because of the exceptions to comprehensive recognition of deferred taxes related to bad debt reserve for tax purposes of a qualified lender.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 942
-SubTopic 740
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
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- Definition

Amount of operating loss carryforward, before tax effects, available to reduce future taxable income under enacted tax laws.

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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
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-Publisher FASB
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- Definition

The amount of the tax credit carryforward, before tax effects, available to reduce future taxable income under enacted tax laws.

+ References

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- Definition

Amount of interest expense accrued for an underpayment of income taxes.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 15
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482685/740-10-50-15

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- Definition

The total amount of unrecognized tax benefits that, if recognized, would affect the effective tax rate.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
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Income Taxes - Additional Information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Income Taxes [Line Items]
Net capital loss carryforwards	$ 4,000,000
Valuation allowances	5,000,000	$ 15,000,000
Deferred tax asset	1,854,000,000	2,437,000,000
Unrecognized tax benefits	3,000,000	39,000,000	$ 45,000,000	$ 40,000,000
Net interest expense (benefit)	(16,000,000)	(1,000,000)	(4,000,000)
Recovery of penalties related to unrecognized tax benefits in income tax expense	0	0	0
Accrued interest payable	1,000,000	$ 1,000,000	$ 600,000
Capital Loss Carryforward
Income Taxes [Line Items]
Valuation allowances	4,000,000
First Niagara Bank, N.A.
Income Taxes [Line Items]
Allocated bad debt deductions for which no income taxes have been recorded	92,000,000
Federal
Income Taxes [Line Items]
Operating loss carryforwards	0
Credit carryforward	226,000,000
Federal \| General Business Tax Credit Carryforward
Income Taxes [Line Items]
Credit carryforward	226,000,000
State
Income Taxes [Line Items]
Valuation allowances	1,000,000
Operating loss carryforwards	80,000,000
Credit carryforward	2,000,000
Deferred tax asset	$ 3,000,000