Benefit Plans - Summary of the Components of Net Periodic Benefit Cost (Details) - Heritage BBT - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Net periodic pension cost:
Service cost	$ 214	$ 238	$ 200
Interest cost	226	201	192
Estimated return on plan assets	460	448	372
Net amortization and other	(111)	(81)	(75)
Net periodic benefit cost	91	72	95
Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss), after Reclassification Adjustment, before Tax	(48)	208	92
Defined Benefit Plan, Amounts Recognized in Other Comprehensive Income (Loss) [Abstract]
Prior service credit (cost)	0	0	(30)
Net actuarial loss (gain)	62	289	137
Net amortization	110	81	75
Total net periodic pension costs (income) recognized in total comprehensive income, pre-tax	$ 43	$ 280	$ 187
Weighted average assumptions used to determine net periodic pension cost:
Discount rate	4.43%	3.79%	4.43%
Expected long-term rate of return on plan assets	7.00%	7.00%	7.00%
Assumed long-term rate of annual compensation increases	4.50%	4.50%	4.50%