Fair Value Part 3 (Details) (USD $)	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Dec. 31, 2013	Dec. 31, 2012
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities held to maturity	$ 1,155,569,000		$ 1,168,728,000
Net LHFI	5,856,248,000		5,732,433,000
FDIC indemnification asset	13,487,000	20,198,000	14,347,000	21,774,000
Deposits	10,122,119,000		9,859,902,000
Long-term FHLB advances	8,341,000		8,458,000
Subordinated notes	49,912,000		49,904,000
Junior subordinated debt securities	61,856,000		61,856,000
Nonfinancial Assets and Liabilities [Abstract]
Outstanding balances in impaired loans	27,600,000		31,600,000
Foreclosed assets measured at fair value	13,700,000	50,000,000
Allowance for possible loan losses, Charge-offs for foreclosed assets upon initial recognition	5,100,000	1,300,000
Foreclosed assets re-measured after initial recognition	7,600,000	13,200,000
Write-downs of allowance for foreclosed assets after initial recognition	1,100,000	1,600,000
Estimated fair value of financial instruments with immediate and shorter-term maturities maximum	90 days
BancTrust Financial Group, Inc. [Member]
Nonfinancial Assets and Liabilities [Abstract]
Foreclosed assets measured at fair value		41,200,000
Level 2 [Member] | Carrying Value [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and short-term investments	423,819,000		353,014,000
Securities held to maturity	1,155,569,000		1,168,728,000
Deposits	10,122,119,000		9,859,902,000
Short-term liabilities	319,012,000		317,972,000
Long-term FHLB advances	8,341,000		8,458,000
Subordinated notes	49,912,000		49,904,000
Junior subordinated debt securities	61,856,000		61,856,000
Level 2 [Member] | Estimate of Fair Value [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and short-term investments	423,819,000		353,014,000
Securities held to maturity	1,154,606,000		1,150,833,000
Deposits	10,126,897,000		9,866,118,000
Short-term liabilities	319,012,000		317,972,000
Long-term FHLB advances	8,358,000		8,474,000
Subordinated notes	53,783,000		53,387,000
Junior subordinated debt securities	40,206,000		40,206,000
Level 3 [Member] | Carrying Value [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net LHFI	5,856,248,000		5,732,433,000
Net acquired loans	735,777,000		794,570,000
FDIC indemnification asset	13,487,000		14,347,000
Level 3 [Member] | Estimate of Fair Value [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net LHFI	5,894,453,000		5,787,408,000
Net acquired loans	735,777,000		794,570,000
FDIC indemnification asset	$ 13,487,000		$ 14,347,000