Income Taxes - Narrative (Details) - USD ($)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Income Taxes [Line Items]
Net capital loss carryforwards	$ 12,000,000
Valuation allowances	12,000,000	$ 0
Credit carryforward	6,000,000	7,000,000
Deferred tax asset	1,100,000,000	1,164,000,000
Unrecognized tax benefits	50,000,000	58,000,000	$ 19,000,000
Net interest expense (benefit)	100,000	200,000	900,000
Recovery of penalties related to unrecognized tax benefits in income tax expense	0	0	$ 0
Accrued interest payable	2,000,000	3,000,000
Accrued state tax penalties	0	$ 0
Reduction in federal tax credit carryforward	0
Maximum
Income Taxes [Line Items]
Valuation allowances	12,000,000
Federal
Income Taxes [Line Items]
Federal net operating loss carryforwards	20,000,000
Credit carryforward	1,000,000
State
Income Taxes [Line Items]
State net operating loss carryforwards	24,000,000
Deferred tax asset	1,000,000
First Niagara Bank, N.A.
Income Taxes [Line Items]
Allocated bad debt deductions for which no income taxes have been recorded	$ 92,000,000