Fair Value (Details 3) (USD $)	Sep. 30, 2013	Dec. 31, 2012	Sep. 30, 2012
Financial liabilities:
Federal funds purchased and securities sold under agreements to repurchase	$ 233,792,000	$ 238,621,000	$ 226,330,000
Other borrowings	101,347,000	54,897,000	45,807,000
Fair Value
Financial assets:
Cash and cash equivalents	645,171,000	380,730,000	278,064,000
Investment securities	654,176,000	561,204,000	501,769,000
Loans, net of allowance for loan losses, and loans held for sale	5,763,726,000	3,665,070,000	3,077,060,000
FDIC receivable for loss share agreements	77,465,000	101,898,000	104,231,000
Accrued interest receivable	15,000,000	8,190,000	10,487,000
Mortgage servicing rights	18,908,000
Interest rate swap - non-designated hedge	209,000	312,000
Financial liabilities:
Deposits	6,410,356,000	4,216,800,000	3,525,346,000
Federal funds purchased and securities sold under agreements to repurchase	233,792,000	238,621,000	226,330,000
Other borrowings	104,984,000	57,903,000	47,826,000
Accrued interest payable	5,489,000	2,045,000	1,921,000
Interest rate swap - cash flow hedge	1,050,000	1,501,000	1,579,000
Interest rate swap - non-designated hedge	209,000	312,000
Fair Value | Commitments to extend credit
Financial liabilities:
Off balance sheet financial instruments	5,985,000	7,371,000	9,715,000
Fair Value | Other derivative financial instruments (Mortgage - banking related)
Financial assets:
Other derivative financial instruments (Mortgage - banking related)	1,101,000
Level 1
Financial assets:
Cash and cash equivalents	645,171,000	380,730,000	278,064,000
Investment securities	17,082,000	10,122,000	8,344,000
Level 1 | Other derivative financial instruments (Mortgage - banking related)
Financial assets:
Other derivative financial instruments (Mortgage - banking related)	1,101,000
Level 2
Financial assets:
Investment securities	637,094,000	547,231,000	493,425,000
Loans, net of allowance for loan losses, and loans held for sale	52,467,000	65,279,000	71,585,000
Accrued interest receivable	3,391,000	8,190,000	10,487,000
Interest rate swap - non-designated hedge	209,000	312,000
Financial liabilities:
Deposits	6,410,356,000	4,216,800,000	3,525,346,000
Federal funds purchased and securities sold under agreements to repurchase	233,792,000	238,621,000	226,330,000
Other borrowings	104,984,000	57,903,000	47,826,000
Accrued interest payable	5,489,000	2,045,000	1,921,000
Interest rate swap - cash flow hedge	1,050,000	1,501,000	1,579,000
Interest rate swap - non-designated hedge	209,000	312,000
Level 2 | Commitments to extend credit
Financial liabilities:
Off balance sheet financial instruments	5,985,000	7,371,000	9,715,000
Level 3
Financial assets:
Investment securities		3,851,000
Loans, net of allowance for loan losses, and loans held for sale	5,711,259,000	3,599,791,000	3,005,475,000
FDIC receivable for loss share agreements	77,465,000	101,898,000	104,231,000
Accrued interest receivable	11,609,000
Mortgage servicing rights	18,908,000
Carrying Amount
Financial assets:
Cash and cash equivalents	645,171,000	380,730,000	278,064,000
Investment securities	652,610,000	560,091,000	500,587,000
Loans, net of allowance for loan losses, and loans held for sale	5,739,526,000	3,634,514,000	3,032,351,000
FDIC receivable for loss share agreements	115,773,000	146,171,000	174,321,000
Accrued interest receivable	15,000,000	8,190,000	10,487,000
Mortgage servicing rights	18,908,000
Interest rate swap - non-designated hedge	209,000	312,000
Financial liabilities:
Deposits	6,663,106,000	4,298,360,000	3,589,298,000
Federal funds purchased and securities sold under agreements to repurchase	233,792,000	238,621,000	226,330,000
Other borrowings	101,347,000	54,897,000	45,807,000
Accrued interest payable	5,489,000	2,045,000	1,921,000
Interest rate swap - cash flow hedge	1,050,000	1,501,000	1,579,000
Interest rate swap - non-designated hedge	209,000	312,000
Carrying Amount | Other derivative financial instruments (Mortgage - banking related)
Financial assets:
Other derivative financial instruments (Mortgage - banking related)	$ 1,101,000