LOANS AND ALLOWANCE FOR LOAN LOSSES (Details 6) (USD $)	Sep. 30, 2014
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-59 days past due	$ 16,830,000
60-89 days past due	17,801,000
Greater Than 90 Days and Accruing	6,102,000	[1]
Total past due	40,733,000
Current	13,437,992,000
Total	13,478,725,000
Premium finance loans past due 90 days and still accruing	5,300,000
Commercial | Business loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-59 days past due	14,300,000
60-89 days past due	7,212,000
Greater Than 90 Days and Accruing	5,914,000	[1]
Total past due	27,426,000
Current	4,635,514,000
Total	4,662,940,000
Commercial | Energy
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-59 days past due	0
60-89 days past due	0
Greater Than 90 Days and Accruing	0	[1]
Total past due	0
Current	933,390,000
Total	933,390,000
Mortgage finance loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-59 days past due	0
60-89 days past due	0
Greater Than 90 Days and Accruing	0	[1]
Total past due	0
Current	3,774,467,000
Total	3,774,467,000
Construction | Market risk
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-59 days past due	983,000
60-89 days past due	2,135,000
Greater Than 90 Days and Accruing	0	[1]
Total past due	3,118,000
Current	1,615,725,000
Total	1,618,843,000
Construction | Secured by 1-4 family
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-59 days past due	0
60-89 days past due	0
Greater Than 90 Days and Accruing	0	[1]
Total past due	0
Current	21,753,000
Total	21,753,000
Real estate | Market risk
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-59 days past due	1,395,000
60-89 days past due	2,949,000
Greater Than 90 Days and Accruing	0	[1]
Total past due	4,344,000
Current	1,782,450,000
Total	1,786,794,000
Real estate | Secured by 1-4 family
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-59 days past due	0
60-89 days past due	41,000
Greater Than 90 Days and Accruing	110,000	[1]
Total past due	151,000
Current	87,581,000
Total	87,732,000
Real estate | Commercial
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-59 days past due	0
60-89 days past due	5,375,000
Greater Than 90 Days and Accruing	78,000	[1]
Total past due	5,453,000
Current	469,534,000
Total	474,987,000
Consumer
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-59 days past due	152,000
60-89 days past due	62,000
Greater Than 90 Days and Accruing	0	[1]
Total past due	214,000
Current	16,288,000
Total	16,502,000
Leases
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-59 days past due	0
60-89 days past due	27,000
Greater Than 90 Days and Accruing	0	[1]
Total past due	27,000
Current	101,290,000
Total	$ 101,317,000

[1] Loans past due 90 days and still accruing includes premium finance loans of $5.3 million. These loans are generally secured by obligations of insurance carriers to refund premiums on canceled insurance policies. The refund of premiums from the insurance carriers can take 180 days or longer from the cancellation date.