Fair Value Part 3 (Details) (USD $)	9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Dec. 31, 2013	Dec. 31, 2012
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities held to maturity	$ 1,169,640,000		$ 1,168,728,000
Net LHFI	6,263,517,000		5,732,433,000
FDIC indemnification asset	8,154,000	17,085,000	14,347,000	21,774,000
Deposits	9,513,225,000		9,859,902,000
Long-term FHLB advances	8,003,000		8,458,000
Subordinated notes	49,928,000		49,904,000
Junior subordinated debt securities	61,856,000		61,856,000
Nonfinancial Assets and Liabilities [Abstract]
Outstanding balances in impaired loans	54,100,000		31,600,000
Foreclosed assets measured at fair value	30,000,000	73,900,000
Allowance for possible loan losses, Charge-offs for foreclosed assets upon initial recognition	9,300,000	9,200,000
Foreclosed assets re-measured after initial recognition	40,600,000	35,000,000
Write-downs of allowance for foreclosed assets after initial recognition	4,800,000	6,100,000
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		40,100,000
Level 2 [Member] | Carrying Value [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and short-term investments	241,510,000		353,014,000
Securities held to maturity	1,169,640,000		1,168,728,000
Deposits	9,513,225,000		9,859,902,000
Short-term liabilities	924,517,000		317,972,000
Long-term FHLB advances	8,003,000		8,458,000
Subordinated notes	49,928,000		49,904,000
Junior subordinated debt securities	61,856,000		61,856,000
Level 2 [Member] | Estimate Fair Value [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and short-term investments	241,510,000		353,014,000
Securities held to maturity	1,170,213,000		1,150,833,000
Deposits	9,518,584,000		9,866,118,000
Short-term liabilities	924,517,000		317,972,000
Long-term FHLB advances	8,014,000		8,474,000
Subordinated notes	53,665,000		53,387,000
Junior subordinated debt securities	46,392,000		40,206,000
Level 3 [Member] | Carrying Value [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net LHFI	6,263,517,000		5,732,433,000
Net acquired loans	580,200,000		794,570,000
FDIC indemnification asset	8,154,000		14,347,000
Level 3 [Member] | Estimate Fair Value [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net LHFI	6,348,938,000		5,787,408,000
Net acquired loans	580,200,000		794,570,000
FDIC indemnification asset	$ 8,154,000		$ 14,347,000