GOODWILL AND OTHER INTANGIBLE ASSETS (Details) (USD $)	3 Months Ended		6 Months Ended					3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013	Dec. 31, 2013	Dec. 31, 2012	Jan. 17, 2014 MetroCorp	Jun. 30, 2014 Premiums on acquired deposits	Jun. 30, 2013 Premiums on acquired deposits	Jun. 30, 2014 Premiums on acquired deposits	Jun. 30, 2013 Premiums on acquired deposits	Dec. 31, 2013 Premiums on acquired deposits
GOODWILL AND OTHER INTANGIBLE ASSETS
Goodwill	$ 458,467,000	$ 337,438,000	$ 458,467,000	$ 337,438,000	$ 337,438,000		$ 121,000,000
Market capitalization	5,020,000,000		5,020,000,000
Total stockholders' equity	2,701,024,000	2,257,951,000	2,701,024,000	2,257,951,000	2,364,225,000	2,382,122,000
Premiums on Acquired Deposits
Gross carrying amount of premiums on acquired deposits								108,800,000		108,800,000		100,200,000
Intangible recorded due to the acquisition of MetroCorp							8,600,000
Accumulated amortization for premiums on acquired deposits								58,400,000		58,400,000		53,300,000
Amortization expense of premiums on acquired deposits	2,624,000	2,375,000	5,124,000	4,784,000				2,624,000	2,375,000	5,124,000	4,784,000
Estimated Future Amortization Expense of Premiums on Acquired Deposits
Six Months Ending December 31, 2014	5,080,000		5,080,000
Year Ending December 31, 2015	9,234,000		9,234,000
Year Ending December 31, 2016	8,086,000		8,086,000
Year Ending December 31, 2017	6,935,000		6,935,000
Year Ending December 31, 2018	5,883,000		5,883,000
Thereafter	15,171,000		15,171,000
Total	$ 50,389,000		$ 50,389,000