Plan Assets Related to Pension and OPB Benefits by Level within the Fair Value Hierarchy (Detail) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2015		Dec. 31, 2014		Dec. 31, 2013
Document Period End Date		Dec. 31, 2015
Defined Benefit Plan, Fair Value of Plan Assets		$ 3,025	[1]	$ 3,223	[2]
Defined Benefit Plan Income Accrued On Plan Assets		0.40%		0.60%
Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan, Fair Value of Plan Assets		$ 1,655	[1]	$ 1,873	[2]
Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plan, Fair Value of Plan Assets		1,370	[1]	1,350	[2]
Fair Value, Inputs, Level 3 [Member]
Defined Benefit Plan, Fair Value of Plan Assets		0		0
Money Market Funds [Member]
Defined Benefit Plan, Fair Value of Plan Assets		83	[1],[3]	135	[2],[4]
Money Market Funds [Member] | Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan, Fair Value of Plan Assets		83	[1],[3]	135	[2],[4]
Money Market Funds [Member] | Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plan, Fair Value of Plan Assets		0		0
Money Market Funds [Member] | Fair Value, Inputs, Level 3 [Member]
Defined Benefit Plan, Fair Value of Plan Assets		0		0
Pension Plan [Member]
Defined Benefit Plan, Fair Value of Plan Assets	[5]	2,879	[6]	3,080	[6]	$ 2,873
Pension Plan [Member] | Equity Securities [Member]
Defined Benefit Plan, Fair Value of Plan Assets		1,416	[1]	1,467	[2]
Pension Plan [Member] | Equity Securities [Member] | Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan, Fair Value of Plan Assets		1,416	[1]	1,467	[2]
Pension Plan [Member] | Equity Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plan, Fair Value of Plan Assets		0		0
Pension Plan [Member] | Equity Securities [Member] | Fair Value, Inputs, Level 3 [Member]
Defined Benefit Plan, Fair Value of Plan Assets		0		0
Pension Plan [Member] | Future [Member]
Defined Benefit Plan, Fair Value of Plan Assets		(11)	[1]	(21)	[2]
Pension Plan [Member] | Future [Member] | Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan, Fair Value of Plan Assets		0		0
Pension Plan [Member] | Future [Member] | Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plan, Fair Value of Plan Assets		(11)	[1]	(21)	[2]
Pension Plan [Member] | Future [Member] | Fair Value, Inputs, Level 3 [Member]
Defined Benefit Plan, Fair Value of Plan Assets		0		0
Pension Plan [Member] | Fixed Income Securities [Member]
Defined Benefit Plan, Fair Value of Plan Assets		1,381	[1]	1,478	[2]
Pension Plan [Member] | Fixed Income Securities [Member] | Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan, Fair Value of Plan Assets		0		107	[2]
Pension Plan [Member] | Fixed Income Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plan, Fair Value of Plan Assets		1,381	[1]	1,371	[2]
Pension Plan [Member] | Fixed Income Securities [Member] | Fair Value, Inputs, Level 3 [Member]
Defined Benefit Plan, Fair Value of Plan Assets		0		0
Pension Plan [Member] | Other Assets [Member]
Defined Benefit Plan, Fair Value of Plan Assets		11	[1]	17	[2]
Pension Plan [Member] | Other Assets [Member] | Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan, Fair Value of Plan Assets		11	[1]	17	[2]
Pension Plan [Member] | Other Assets [Member] | Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plan, Fair Value of Plan Assets		0		0
Pension Plan [Member] | Other Assets [Member] | Fair Value, Inputs, Level 3 [Member]
Defined Benefit Plan, Fair Value of Plan Assets		0		0
Other Postretirement Benefit Plan [Member]
Defined Benefit Plan, Fair Value of Plan Assets		156	[6]	160	[6]	$ 158
Other Postretirement Benefit Plan [Member] | Money Market Funds [Member] | Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan, Fair Value of Plan Assets		11		13
Other Postretirement Benefit Plan [Member] | Equity Funds [Member]
Defined Benefit Plan, Fair Value of Plan Assets		48	[1],[7]	51	[2],[8]
Other Postretirement Benefit Plan [Member] | Equity Funds [Member] | Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan, Fair Value of Plan Assets		48	[1],[7]	51	[2],[8]
Other Postretirement Benefit Plan [Member] | Equity Funds [Member] | Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plan, Fair Value of Plan Assets		0		0
Other Postretirement Benefit Plan [Member] | Equity Funds [Member] | Fair Value, Inputs, Level 3 [Member]
Defined Benefit Plan, Fair Value of Plan Assets		0		0
Other Postretirement Benefit Plan [Member] | Nontaxable Municipal Bonds [Member]
Defined Benefit Plan, Fair Value of Plan Assets		84	[1],[7]	82	[2],[8]
Other Postretirement Benefit Plan [Member] | Nontaxable Municipal Bonds [Member] | Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan, Fair Value of Plan Assets		84	[1],[7]	82	[2],[8]
Other Postretirement Benefit Plan [Member] | Nontaxable Municipal Bonds [Member] | Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plan, Fair Value of Plan Assets		0		0
Other Postretirement Benefit Plan [Member] | Nontaxable Municipal Bonds [Member] | Fair Value, Inputs, Level 3 [Member]
Defined Benefit Plan, Fair Value of Plan Assets		0		0
Other Postretirement Benefit Plan [Member] | Taxable Fixed Income Index Funds [Member]
Defined Benefit Plan, Fair Value of Plan Assets		13	[1],[7]	14	[2],[8]
Other Postretirement Benefit Plan [Member] | Taxable Fixed Income Index Funds [Member] | Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan, Fair Value of Plan Assets		13	[1],[7]	14	[2],[8]
Other Postretirement Benefit Plan [Member] | Taxable Fixed Income Index Funds [Member] | Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plan, Fair Value of Plan Assets		0		0
Other Postretirement Benefit Plan [Member] | Taxable Fixed Income Index Funds [Member] | Fair Value, Inputs, Level 3 [Member]
Defined Benefit Plan, Fair Value of Plan Assets		$ 0		$ 0

[1] Fair value measurements do not include pension benefits accrued income amounting to less than 0.4% 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] Includes $11 million for other postretirement benefit plans.

[4] Includes $13 million for other postretirement benefit plans.

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

[6] Includes $1 million of the Company's common stock acquired by the asset manager and held as part of the equity portfolio for pension benefits at both December 31, 2015 and 2014. During 2015 and 2014, there was no SunTrust common stock held in the other postretirement benefit plans.

[7] Relates exclusively to other postretirement benefit plans.

[8] Relates exclusively to other postretirement benefit plans.