Plan Assets Related to Other Postretirement Benefits by Level within the Fair Value Hierarchy (Detail) (Other Postretirement Benefit Plans, Defined Benefit, USD $) In Millions, unless otherwise specified	Dec. 31, 2012		Dec. 31, 2011		Dec. 31, 2010
Plan assets	$ 164	[1]	$ 161	[2]	$ 165
Fair Value, Inputs, Level 1 [Member]
Plan assets	164	[1]	68	[2]
Fair Value, Inputs, Level 2 [Member]
Plan assets	0	[1]	93	[2]
Fair Value, Inputs, Level 3 [Member]
Plan assets	0	[1]	0	[2]
Equity Mutual Funds [Member]
Plan assets	49	[1]
Equity Mutual Funds [Member] | Large Cap Funds
Plan assets			37	[2]
Equity Mutual Funds [Member] | Tax Exempt Fixed Maturities
Plan assets			25	[2]
Equity Mutual Funds [Member] | International
Plan assets			6	[2]
Equity Mutual Funds [Member] | Fair Value, Inputs, Level 1 [Member]
Plan assets	49	[1]
Equity Mutual Funds [Member] | Fair Value, Inputs, Level 1 [Member] | Large Cap Funds
Plan assets			37	[2]
Equity Mutual Funds [Member] | Fair Value, Inputs, Level 1 [Member] | Tax Exempt Fixed Maturities
Plan assets			25	[2]
Equity Mutual Funds [Member] | Fair Value, Inputs, Level 1 [Member] | International
Plan assets			6	[2]
Equity Mutual Funds [Member] | Fair Value, Inputs, Level 2 [Member]
Plan assets	0	[1]
Equity Mutual Funds [Member] | Fair Value, Inputs, Level 2 [Member] | Large Cap Funds
Plan assets			0	[2]
Equity Mutual Funds [Member] | Fair Value, Inputs, Level 2 [Member] | Tax Exempt Fixed Maturities
Plan assets			0	[2]
Equity Mutual Funds [Member] | Fair Value, Inputs, Level 2 [Member] | International
Plan assets			0	[2]
Equity Mutual Funds [Member] | Fair Value, Inputs, Level 3 [Member]
Plan assets	0	[1]
Equity Mutual Funds [Member] | Fair Value, Inputs, Level 3 [Member] | Large Cap Funds
Plan assets			0	[2]
Equity Mutual Funds [Member] | Fair Value, Inputs, Level 3 [Member] | Tax Exempt Fixed Maturities
Plan assets			0	[2]
Equity Mutual Funds [Member] | Fair Value, Inputs, Level 3 [Member] | International
Plan assets			0	[2]
Nontaxable Municipal Bonds [Member]
Plan assets	86	[1]
Nontaxable Municipal Bonds [Member] | Fair Value, Inputs, Level 1 [Member]
Plan assets	86	[1]
Nontaxable Municipal Bonds [Member] | Fair Value, Inputs, Level 2 [Member]
Plan assets	0	[1]
Nontaxable Municipal Bonds [Member] | Fair Value, Inputs, Level 3 [Member]
Plan assets	0	[1]
Taxable Fixed Income Index Funds [Member]
Plan assets	14	[1]
Taxable Fixed Income Index Funds [Member] | Fair Value, Inputs, Level 1 [Member]
Plan assets	14	[1]
Taxable Fixed Income Index Funds [Member] | Fair Value, Inputs, Level 2 [Member]
Plan assets	0	[1]
Taxable Fixed Income Index Funds [Member] | Fair Value, Inputs, Level 3 [Member]
Plan assets	0	[1]
Money Market Funds [Member]
Plan assets	15	[1]
Money Market Funds [Member] | Fair Value, Inputs, Level 1 [Member]
Plan assets	15	[1]
Money Market Funds [Member] | Fair Value, Inputs, Level 2 [Member]
Plan assets	0	[1]
Money Market Funds [Member] | Fair Value, Inputs, Level 3 [Member]
Plan assets	0	[1]
Common And Collective Funds | SunTrust Reserve Fund
Plan assets			1	[2]
Common And Collective Funds | SunTrust Equity Fund
Plan assets			37	[2]
Common And Collective Funds | SunTrust Georgia Tax-Free Fund
Plan assets			26	[2]
Common And Collective Funds | SunTrust National Tax-Free Fund
Plan assets			17	[2]
Common And Collective Funds | SunTrust Aggregate Fixed Income Fund
Plan assets			7	[2]
Common And Collective Funds | SunTrust Short Term Bond Fund
Plan assets			5	[2]
Common And Collective Funds | Fair Value, Inputs, Level 1 [Member] | SunTrust Reserve Fund
Plan assets			0	[2]
Common And Collective Funds | Fair Value, Inputs, Level 1 [Member] | SunTrust Equity Fund
Plan assets			0	[2]
Common And Collective Funds | Fair Value, Inputs, Level 1 [Member] | SunTrust Georgia Tax-Free Fund
Plan assets			0	[2]
Common And Collective Funds | Fair Value, Inputs, Level 1 [Member] | SunTrust National Tax-Free Fund
Plan assets			0	[2]
Common And Collective Funds | Fair Value, Inputs, Level 1 [Member] | SunTrust Aggregate Fixed Income Fund
Plan assets			0	[2]
Common And Collective Funds | Fair Value, Inputs, Level 1 [Member] | SunTrust Short Term Bond Fund
Plan assets			0	[2]
Common And Collective Funds | Fair Value, Inputs, Level 2 [Member] | SunTrust Reserve Fund
Plan assets			1	[2]
Common And Collective Funds | Fair Value, Inputs, Level 2 [Member] | SunTrust Equity Fund
Plan assets			37	[2]
Common And Collective Funds | Fair Value, Inputs, Level 2 [Member] | SunTrust Georgia Tax-Free Fund
Plan assets			26	[2]
Common And Collective Funds | Fair Value, Inputs, Level 2 [Member] | SunTrust National Tax-Free Fund
Plan assets			17	[2]
Common And Collective Funds | Fair Value, Inputs, Level 2 [Member] | SunTrust Aggregate Fixed Income Fund
Plan assets			7	[2]
Common And Collective Funds | Fair Value, Inputs, Level 2 [Member] | SunTrust Short Term Bond Fund
Plan assets			5	[2]
Common And Collective Funds | Fair Value, Inputs, Level 3 [Member] | SunTrust Reserve Fund
Plan assets			0	[2]
Common And Collective Funds | Fair Value, Inputs, Level 3 [Member] | SunTrust Equity Fund
Plan assets			0	[2]
Common And Collective Funds | Fair Value, Inputs, Level 3 [Member] | SunTrust Georgia Tax-Free Fund
Plan assets			0	[2]
Common And Collective Funds | Fair Value, Inputs, Level 3 [Member] | SunTrust National Tax-Free Fund
Plan assets			0	[2]
Common And Collective Funds | Fair Value, Inputs, Level 3 [Member] | SunTrust Aggregate Fixed Income Fund
Plan assets			0	[2]
Common And Collective Funds | Fair Value, Inputs, Level 3 [Member] | SunTrust Short Term Bond Fund
Plan assets			$ 0	[2]

[1] Schedule does not include accrued income. Fair ValueMeasurements as ofDecember 31, 2011 1(Dollars in millions)Assets Measuredat Fair Value asof December 31,2011 Quoted Prices InActive Marketsfor IdenticalAssets (Level 1) SignificantOtherObservableInputs(Level 2) SignificantUnobservableInputs(Level 3)Mutual funds: Large cap fund $37 $37 $— $—Investment grade tax-exempt bond 25 25 — —International fund 6 6 — —Common and collective funds: SunTrust Reserve Fund 1 — 1 —SunTrust Equity Fund 37 — 37 —SunTrust Georgia Tax-Free Fund 26 — 26 —SunTrust National Tax-Free Fund 17 — 17 —SunTrust Aggregate Fixed Income Fund 7 — 7 —SunTrust Short-Term Bond Fund 5 — 5 —Total plan assets $161 $68 $93 $—

[2] Schedule does not include accrued income.