Regulatory Capital Requirements (Capital and Risk-Based Capital and Leverage Ratios for the Bancorp and its Significant Subsidiary Banks) (Detail) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Fifth Third Bancorp
Risk Based Ratios
CET1 capital (to risk-weighted assets)	10.61%	10.39%
Tier I risk-based capital (to risk-weighted assets)	11.74%	11.50%
Total risk-based capital (to risk-weighted assets)	15.16%	15.02%
Tier I leverage (to quarterly average assets)	10.01%	9.90%
Risk Based Capital
CET1 capital (to risk-weighted assets)	$ 12,517	$ 12,426
Tier I risk-based capital (to risk-weighted assets)	13,848	13,756
Total risk-based capital (to risk weighted assets)	17,887	17,972
Tier I leverage (to quarterly average assets)	$ 13,848	$ 13,756
Fifth Third Bank
Risk Based Ratios
CET1 capital (to risk-weighted assets)	12.06%	11.92%
Tier I risk-based capital (to risk-weighted assets)	12.06%	11.92%
Total risk-based capital (to risk-weighted assets)	13.88%	13.76%
Tier I leverage (to quarterly average assets)	10.32%	10.30%
Risk Based Capital
CET1 capital (to risk-weighted assets)	$ 14,008	$ 14,015
Tier I risk-based capital (to risk-weighted assets)	14,008	14,015
Total risk-based capital (to risk weighted assets)	16,126	16,175
Tier I leverage (to quarterly average assets)	$ 14,008	$ 14,015
Minimum
Risk Based Ratios
CET1 capital (to risk-weighted assets)	4.50%
Tier I risk-based capital (to risk-weighted assets)	6.00%
Total risk-based capital (to risk-weighted assets)	8.00%
Tier I leverage (to quarterly average assets)	4.00%
Well-capitalized
Risk Based Ratios
CET1 capital (to risk-weighted assets)	6.50%
Tier I risk-based capital (to risk-weighted assets)	8.00%
Total risk-based capital (to risk-weighted assets)	10.00%
Tier I leverage (to quarterly average assets)	5.00%