Retirement and Benefit Plans - Retirement and Benefit Plans - Additional Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Defined Benefit Plan Disclosure
Increase in pension expense by lowering both the expected rate of return on the plan and the discount rate by 0.25%	$ 1
Estimated future defined benefit plan contributions	2
Estimated pension benefit payments for 2021	18
Estimated pension benefit payments for 2022	17
Estimated pension benefit payments for 2023	18
Estimated pension benefit payments for 2024	16
Estimated pension benefit payments for 2025	18
Estimated pension benefit payments for 2026 through 2030	66
Plan assets	173	$ 175
Qualified defined contribution plan
Defined Benefit Plan Disclosure
Expenses recognized for the Bancorp's defined contribution plan	105	90	$ 83
Non-qualified defined contribution plan
Defined Benefit Plan Disclosure
Expenses recognized for the Bancorp's defined contribution plan	5	6	4
Deferred profit sharing
Defined Benefit Plan Disclosure
Expenses recognized for the Bancorp's defined contribution plan	0	4	$ 0
Fifth Third Bank, National Association
Defined Benefit Plan Disclosure
Plan assets	$ 173	$ 175