Acquisitions and Divestitures - Narrative (Details) $ in Millions		12 Months Ended
	Jul. 01, 2020 USD ($) numberNewPreferredStockSeries state office shares	Dec. 31, 2020 USD ($) shares	Jun. 30, 2021 USD ($) shares	Jul. 17, 2020 USD ($) branch	Jun. 30, 2020 USD ($)	Dec. 31, 2019 USD ($)
Business Acquisition [Line Items]
Number of common stock issued (in shares) | shares	243,000,000	555,030,652	550,865,126
Number of new series of preferred stock | numberNewPreferredStockSeries	3
Goodwill		$ 1,511	$ 1,511		$ 1,511	$ 1,433
IBERIABANK (IBKC)
Business Acquisition [Line Items]
Equity interest issued, value assigned	$ 2,500
Purchase accounting gain	531	531
Goodwill	$ (531)
Truist Bank Branches
Business Acquisition [Line Items]
Number of bank branches | branch				30
Goodwill		$ 78		$ 78
IBERIABANK (IBKC)
Business Acquisition [Line Items]
Number of offices | office	319
Number of states | state	12