Benefit Plans - Changes in Projected Benefit Obligations (Inactive Plan) - (Details) - USD ($) $ in Millions	1 Months Ended	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Heritage BBT
Defined Benefit Plan Disclosure [Line Items]
Service cost		$ 214	$ 238	$ 200
Heritage BBT | Qualified Plan
Defined Benefit Plan Disclosure [Line Items]
Projected benefit obligation, beginning balance		4,697	4,939
Service cost		199	222
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)		(1,049)	537
Defined Benefit Plan, Benefit Obligation, Benefits Paid		125	113
Accumulated benefit obligation, end of year	$ 5,069	$ 5,069	$ 4,035
Weighted average assumed discount rate	3.45%	3.45%	4.43%
Projected benefit obligation, ending balance	$ 6,029	$ 6,029	$ 4,697	4,939
Heritage BBT | Nonqualified Plans
Defined Benefit Plan Disclosure [Line Items]
Projected benefit obligation, beginning balance		386	387
Service cost		15	16
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)		(79)	19
Defined Benefit Plan, Benefit Obligation, Benefits Paid		13	13
Accumulated benefit obligation, end of year	$ 359	$ 359	$ 293
Weighted average assumed discount rate	3.45%	3.45%	4.43%
Projected benefit obligation, ending balance	$ 484	$ 484	$ 386	$ 387
SunTrust Banks Inc. | Qualified Plan
Defined Benefit Plan Disclosure [Line Items]
Projected benefit obligation, beginning balance		2,800
Service cost	7
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)	(7)
Defined Benefit Plan, Benefit Obligation, Benefits Paid	10
Defined Benefit Plan, Cost of Providing Special and Contractual Termination Benefits	0
Accumulated benefit obligation, end of year	$ 2,790	$ 2,790
Weighted average assumed discount rate	3.22%	3.22%
Projected benefit obligation, ending balance	$ 2,790	$ 2,790	2,800
SunTrust Banks Inc. | Nonqualified Plans
Defined Benefit Plan Disclosure [Line Items]
Projected benefit obligation, beginning balance		72
Service cost	0
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)	0
Defined Benefit Plan, Benefit Obligation, Benefits Paid	0
Defined Benefit Plan, Cost of Providing Special and Contractual Termination Benefits	1
Accumulated benefit obligation, end of year	$ 73	$ 73
Weighted average assumed discount rate	3.22%	3.22%
Projected benefit obligation, ending balance	$ 73	$ 73	$ 72