Contingencies (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Standby Letters of Credit [Member] | Trustmark Corporation [Member]
Loss Contingencies [Line Items]
Maximum potential exposure to credit loss in the event of nonperformance	$ 161.7	$ 178.2
Letters of Credit, Maturity Term - Maximum (in years)	3 Y
Collateral Held, Fair Value	$ 52.0
Pending or Threatened Litigation [Member] | Trustmark National Bank [Member]
Loss Contingencies [Line Items]
Lawsuits Naming Entity as Defendant, number	2