Borrowings, Junior Subordinated Debt Securities (Details) (USD $)	12 Months Ended			0 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Aug. 18, 2006 Quarter
Variable Interest Entity [Line Items]
Junior subordinated debt securities	$ 61,856,000	$ 61,856,000
Total assets	12,250,633,000	11,790,383,000
Total liabilities and shareholders' equity	12,250,633,000	11,790,383,000
Common securities	14,060,000	14,038,000
Net income	123,562,000	117,060,000	117,283,000
Trustmark Preferred Capital Trust I [Member]
Variable Interest Entity [Line Items]
Total assets	61,900,000	61,900,000
Total liabilities and shareholders' equity	61,900,000	61,900,000
Common securities	1,900,000	1,900,000
Net income	36,800	37,600	41,300
Dividends paid	36,800	37,600	41,300
Trustmark Preferred Capital Trust I [Member] | Junior Subordinated Debt Securities [Member]
Variable Interest Entity [Line Items]
Face amount of debt issued				60,000,000
Maturity date				Sep. 30, 2036
Variable interest rate, description				three-month LIBOR
Basis spread over LIBOR rate (in hundredths)				1.72%
Junior subordinated debt securities				$ 61,900,000
Consecutive quarters that Trustmark may defer interest payments				20