Derivative Financial Instruments - Additional Information (Detail) (USD $) Share data in Millions, unless otherwise specified	3 Months Ended	9 Months Ended		3 Months Ended				9 Months Ended					9 Months Ended			9 Months Ended
	Sep. 30, 2008	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2008 Sun Trust Banks, Inc. and Subsidiaries Subsidiaries	Sep. 30, 2008 Sun Trust Bank Subsidiaries	Sep. 30, 2011 Derivatives Sold Credit Default Swap	Dec. 31, 2010 Derivatives Sold Credit Default Swap	Sep. 30, 2011 Lower Limit years	Sep. 30, 2011 Upper Limit years	Sep. 30, 2011 Credit and Market Risk	Dec. 31, 2010 Credit and Market Risk	Sep. 30, 2011 Credit and Market Risk Additional Termination Event [Member]	Sep. 30, 2011 Credit and Market Risk Additional Termination Event [Member] Credit Downgrade [Member]	Sep. 30, 2011 Credit and Market Risk Credit Support Annex	Sep. 30, 2011 Credit and Market Risk Credit Support Annex Credit Downgrade [Member]	Sep. 30, 2011 Credit and Market Risk Credit Support Annex Additional Credit Downgrade [Member]	Sep. 30, 2011 Credit Default Swap	Dec. 31, 2010 Credit Default Swap	Sep. 30, 2011 Credit Derivatives Swap Participation	Dec. 31, 2010 Credit Derivatives Swap Participation	Sep. 30, 2011 Total Return Swap	Dec. 31, 2010 Total Return Swap	Sep. 30, 2011 Cash Flow Hedging
Derivative asset positions										$ 2,500,000,000	$ 1,600,000,000
Net derivative asset positions to which the Company was exposed to risk of its counterparties, netted by counterparty where formal netting arrangements exist										3,900,000,000	2,800,000,000
Collateral held by the Company against derivative asset positions										1,400,000,000	1,200,000,000
Adjusted the fair value of its net derivative asset position for estimates of counterparty credit risk										46,000,000	33,000,000
Posted collateral															16,000,000	10,000,000
Gross notional amounts																	372,000,000	87,000,000			1,400,000,000	969,000,000
Derivative asset positions																					47,000,000	34,000,000
Derivative liability positions										1,200,000,000	1,100,000,000	17,000,000	5,000,000	1,100,000,000							44,000,000	32,000,000
Collateral held																					318,000,000	268,000,000
Posted collateral													3,000,000	1,000,000,000
Senior long-term debt ratings from three of the major ratings agencies										A3/BBB+			Baa3/BBB-			Ba1/BB+
Derivative remaining terms, lower limit																	1 year		1 month				2 years
Derivative remaining terms, higher limit																	10 years		7 years				6 years
Weighted average on the maximum estimated exposure (in years)																			P3.4Y				P3.6Y
Deferred net gains on derivatives that are recorded in AOCI are expected to be reclassified to net interest income over the next twelve months in connection with the recognition of interest income or interest expense on these hedged items																							337,000,000
Maximum exposure																	177,000,000	99,000,000	67,000,000	74,000,000
Fair values of written CDS						3,000,000	300,000										9,000,000	1,000,000
Executed equity forward agreements, underlying shares	30.0			22.9	7.1
Probable forecasted sale of Coke								6.5	7.0
Reconized ineffectiveness which was recorded in trading account profits and commissions		$ 1,000,000	$ 9,000,000