Summary of Significant Policies (Summary of Significant Accounting and Reporting Policies - Additional Information) (Detail) - USD ($)	Dec. 31, 2018	Jan. 01, 2018	[1]	Jan. 01, 2016	[2]
Significant Accounting Policies
Established threshold nonaccrual commercial loans	$ 1,000,000
Established threshold impaired loans on accrual status	1,000,000
Larger commercial loans, subject to impairment review	1,000,000
Established threshold commercial loans not subject to specific allowance calculations	1,000,000
Reduction to card and processing revenue	127,000,000
Impact of cumulative effect of change in accounting principles		$ 4,000,000		$ (134,000,000)
Right of use asset and lease liabilities	510,000,000
Leases
Significant Accounting Policies
Impact of cumulative effect of change in accounting principles	$ 13,000,000

[1] Related to the adoption as of January 1, 2018 of ASU 2016-0 1, ASU 2017-12 and ASU 2018-02. Refer to Note 1 for additional information.

[2] Effective in the fourth quarter of 2018, Fifth Third retrospectively applied a change in its accounting policy for investments in affordable housing projects that qualify for LIHTC in accordance with ASU 2014-01. Refer to Note 1 for additional information.