Defined Benefit Plan, Change in Obligations and Fair Value (Detail) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2017		Dec. 31, 2016		Dec. 31, 2015
Defined Benefit Plan, Fair Value of Plan Assets		$ 3,432	[1]	$ 3,156	[2]
Pension Plan [Member]
Defined Benefit Plan, Benefit Obligation	[3]	2,910	[4]	2,747	[4]	$ 2,716
Defined Benefit Plan, Service Cost	[5]	5	[3]	5	[3]	5
Defined Benefit Plan, Interest Cost		95	[3]	97	[3]	116
Defined Benefit Plan, Benefit Obligation, Contributions by Plan Participant	[3]	0		0
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)	[3]	225		76
Defined Benefit Plan, Benefit Obligation, Benefits Paid	[3]	156		142
Defined Benefit Plan, Benefit Obligation, Administrative Expenses	[3]	(6)		(5)
Defined Benefit Plan, Benefit Obligation, Increase (Decrease) for Plan Amendment	[3]	0		0
Defined Benefit Plan, Benefit Obligation, Special and Contractual Termination Benefits	[3]	0		0
Defined Benefit Plan, Fair Value of Plan Assets	[3]	3,288	[6]	3,016	[6]	2,879
Defined Benefit Plan, Plan Assets, Increase (Decrease) for Actual Return (Loss)	[3]	425		279
Defined Benefit Plan, Plan Assets, Contributions by Employer	[3]	9		5
Defined Benefit Plan, Plan Assets, Contributions by Plan Participant	[3]	0		0
Defined Benefit Plan, Plan Assets, Benefits Paid	[3]	(156)		(142)
Defined Benefit Plan, Plan Assets, Administration Expense	[3]	(6)		(5)
Defined Benefit Plan, Funded (Unfunded) Status of Plan	[3],[7]	$ 378		$ 269
Defined Benefit Plan, Funded Percentage	[3]	113.00%		110.00%
Defined Benefit Plan, Accumulated Benefit Obligation	[3]	$ 2,910		$ 2,747
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Discount Rate	[3]	3.62%		4.18%
Other Postretirement Benefits Plan [Member]
Defined Benefit Plan, Benefit Obligation		$ 58	[4]	$ 58	[4]	65
Defined Benefit Plan, Service Cost		0		0		0
Defined Benefit Plan, Interest Cost		1		2		2
Defined Benefit Plan, Benefit Obligation, Contributions by Plan Participant		4		4
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)		(1)		(4)
Defined Benefit Plan, Benefit Obligation, Benefits Paid		8		9
Defined Benefit Plan, Benefit Obligation, Administrative Expenses		0		0
Defined Benefit Plan, Benefit Obligation, Increase (Decrease) for Plan Amendment		(5)		0
Defined Benefit Plan, Benefit Obligation, Special and Contractual Termination Benefits		9		0
Defined Benefit Plan, Fair Value of Plan Assets		164	[6]	157	[6]	$ 156
Defined Benefit Plan, Plan Assets, Increase (Decrease) for Actual Return (Loss)		11		5
Defined Benefit Plan, Plan Assets, Contributions by Employer	[8]	0		0
Defined Benefit Plan, Plan Assets, Benefits Paid		(8)		(9)
Defined Benefit Plan, Plan Assets, Administration Expense		0		0
Defined Benefit Plan, Funded (Unfunded) Status of Plan	[9]	$ 106		$ 99
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Discount Rate		3.29%		3.70%
Market Approach Valuation Technique [Member] | Other Postretirement Benefits Plan [Member]
Defined Benefit Plan, Plan Assets, Contributions by Plan Participant		$ 4		$ 5

[1] Fair value measurements do not include pension benefits accrued income amounting to less than 0.7% of total plan assets.

[2] Fair value measurements do not include pension benefits accrued income amounting to less than 0.6% of total plan assets.

[3] Employer contributions represent the benefits that were paid to nonqualified plan participants. Unfunded nonqualified supplemental pension plans are not funded through plan assets.

[4] Includes $78 million and $80 million of benefit obligations for the unfunded nonqualified supplemental pension plans at December 31, 2017 and 2016, respectively.

[5] Administrative fees are recognized in service cost for each of the periods presented.

[6] Includes $1 million and $2 million of the Company's common stock acquired by the asset manager and held as part of the equity portfolio for pension benefits at December 31, 2017 and 2016, respectively. During both 2017 and 2016, there was no SunTrust common stock held in the other postretirement benefit plans.

[7] Pension benefits recorded in the Consolidated Balance Sheets included other assets of $456 million and $349 million, and other liabilities of $78 million and $80 million, at December 31, 2017 and 2016, respectively.

[8] The Company contributed less than $1 million to the other postretirement benefits plans during both 2017 and 2016.

[9] Other postretirement benefits recorded in the Consolidated Balance Sheets included other assets of $106 million and $99 million at December 31, 2017 and 2016, respectively.