Description of Business, Basis of Presentation and Significant Accounting Policies and Recently Issued Accounting Pronouncements - Premises and Equipment (Details) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Property, Plant and Equipment [Line Items]
Allowance for off-balance sheet financial instruments	$ 306,000,000	$ 306,000,000
Capitalization Threshold Policy, Contractual Lease Payments	$ 25,000
Minimum | Buildings and building improvements
Property, Plant and Equipment [Line Items]
Useful lives	15 years
Minimum | Furniture, fixtures and equipment
Property, Plant and Equipment [Line Items]
Useful lives	3 years
Maximum | Buildings and building improvements
Property, Plant and Equipment [Line Items]
Useful lives	39 years
Maximum | Furniture, fixtures and equipment
Property, Plant and Equipment [Line Items]
Useful lives	7 years