Capital and Risk-Based Capital and Leverage Ratios for the Bancorp and its Significant Subsidiary Banks (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2011		Dec. 31, 2010
Fifth Third Bancorp (Consolidated)
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Total risk-based capital (to risk-weighted assets)	16.09%		18.08%
Tier I capital (to risk-weighted assets)	11.91%		13.89%
Tier I leverage (to average assets)	11.10%		12.79%
Total risk-based capital (to risk weighted assets)	$ 16,885	[1]	$ 18,178	[1]
Tier I capital (to risk-weighted assets)	12,503	[1]	13,965	[1]
Tier I leverage (to average assets)	12,503		13,965
Fifth Third Bank
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Total risk-based capital (to risk-weighted assets)	13.61%		15.12%
Tier I capital (to risk-weighted assets)	12.02%		13.13%
Tier I leverage (to average assets)	11.20%		12.08%
Total risk-based capital (to risk weighted assets)	14,013	[1]	14,936	[1]
Tier I capital (to risk-weighted assets)	12,373	[1]	12,976	[1]
Tier I leverage (to average assets)	$ 12,373		$ 12,976

[1] Under the banking agencies risk-based capital guidelines, assets and credit equivalent amounts of derivatives and off-balance sheet exposures are assigned to broad risk categories. The aggregate dollar amount in each risk category is multiplied by the associated risk weight of the category. The resulting weighted values are added together resulting in the Bancorp’s total risk-weighted assets.