GOODWILL AND OTHER INTANGIBLE ASSETS (Details) (USD $)	3 Months Ended		9 Months Ended				3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013	Dec. 31, 2013	Jan. 17, 2014 MetroCorp	Sep. 30, 2014 Premiums on acquired deposits	Sep. 30, 2013 Premiums on acquired deposits	Sep. 30, 2014 Premiums on acquired deposits	Sep. 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
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							61,000,000		61,000,000		53,300,000
Amortization expense of premiums on acquired deposits	2,597,000	2,347,000	7,721,000	7,131,000			2,600,000	2,300,000	7,700,000	7,100,000
Estimated Future Amortization Expense of Premiums on Acquired Deposits
Three Months Ending December 31, 2014	2,483,000		2,483,000
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	$ 47,792,000		$ 47,792,000