FAIR VALUE - Fair Value (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Assets:
Investment securities available for sale	$ 1,886,395	$ 1,965,666
Less: allowance for loan and lease losses	(240,710)	(222,395)
Derivatives, included in assets	806	39
Liabilities:
Other borrowings	226,492	231,959
Derivatives, included in liabilities	921	187
Carrying Reported Amount Fair Value Disclosure [Member]
Assets:
Cash and due from banks and money market investments	752,458	796,108
Investment securities available for sale	1,886,395	1,965,666
Other equity securities	32,169	25,752
Loans held for sale	35,869	76,956
Loans, held for investment	9,273,865	9,262,436
Less: allowance for loan and lease losses	(240,710)	(222,395)
Loans held for investment, net of allowance	9,033,155	9,040,041
Derivatives, included in assets	806	39
Liabilities:
Deposits	9,338,124	9,483,945
Securities sold under agreements to repurchase	700,000	900,000
Advances from FHLB	455,000	325,000
Notes Payable		0
Other borrowings	226,492	231,959
Derivatives, included in liabilities	921	187
Estimate Of Fair Value Fair Value Disclosure [Member]
Assets:
Cash and due from banks and money market investments	752,458	796,108
Investment securities available for sale	1,886,395	1,965,666
Other equity securities	32,169	25,752
Loans held for sale	36,844	77,888
Loans held for investment, net of allowance	8,899,696	8,844,659
Derivatives, included in assets	806	39
Liabilities:
Deposits	9,334,073	9,486,325
Securities sold under agreements to repurchase	752,048	958,715
Advances from FHLB	453,182	324,376
Notes Payable		0
Other borrowings	142,846	162,344
Derivatives, included in liabilities	921	187
Estimate Of Fair Value Fair Value Disclosure [Member] | Fair Value Inputs Level 1 [Member]
Assets:
Cash and due from banks and money market investments	752,458	796,108
Investment securities available for sale	7,497	7,499
Other equity securities	0	0
Loans held for sale	0	0
Loans held for investment, net of allowance	0	0
Derivatives, included in assets	0	0
Liabilities:
Deposits	0	0
Securities sold under agreements to repurchase	0	0
Advances from FHLB	0	0
Other borrowings	0	0
Derivatives, included in liabilities	0	0
Estimate Of Fair Value Fair Value Disclosure [Member] | Fair Value Inputs Level 2 [Member]
Assets:
Cash and due from banks and money market investments	0	0
Investment securities available for sale	1,851,601	1,921,955
Other equity securities	32,169	25,752
Loans held for sale	28,709	23,247
Loans held for investment, net of allowance	0	0
Derivatives, included in assets	806	39
Liabilities:
Deposits	9,334,073	9,486,325
Securities sold under agreements to repurchase	752,048	958,715
Advances from FHLB	453,182	324,376
Other borrowings	0	0
Derivatives, included in liabilities	921	187
Estimate Of Fair Value Fair Value Disclosure [Member] | Fair Value Inputs Level 3 [Member]
Assets:
Cash and due from banks and money market investments	0	0
Investment securities available for sale	27,297	36,212
Other equity securities	0	0
Loans held for sale	8,135	54,641
Loans held for investment, net of allowance	8,899,696	8,844,659
Derivatives, included in assets	0	0
Liabilities:
Deposits	0	0
Securities sold under agreements to repurchase	0	0
Advances from FHLB	0	0
Other borrowings	142,846	162,344
Derivatives, included in liabilities	$ 0	$ 0