Retirement and Benefit Plans (Retirement and Benefit Plans - Additional Information) (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Defined Benefit Plan Disclosure
The estimated net actuarial loss for the defined benefit pension plans that will be amortized from accumulated other comprehensive income into net periodic benefit cost	$ 6
The increase in pension expense by lowering both the expected rate of return on the plan and the discount rate by 0.25%	1
Defined Benefit Plan Expected Future Benefit Payments in 2019	17
Defined Benefit Plan Expected Future Benefit Payments in 2020	16
Defined Benefit Plan Expected Future Benefit Payments in 2021	16
Defined Benefit Plan Expected Future Benefit Payments in 2022	16
Defined Benefit Plan Expected Future Benefit Payments in 2023	16
Defined Benefit Plan Expected Future Benefit Payments in 2024 through 2028	70
Estimated future defined benefit plan contributions	2
Plan assets	164	$ 185
Deferred profit sharing
Defined Benefit Plan Disclosure
Expenses recognized for the Bancorp's defined contribution plan	0	0	$ 0
Qualified defined contribution plan
Defined Benefit Plan Disclosure
Expenses recognized for the Bancorp's defined contribution plan	83	79	75
Non-qualified defined contribution plan
Defined Benefit Plan Disclosure
Expenses recognized for the Bancorp's defined contribution plan	$ 4	$ 4	$ 3