FAIR VALUE - Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Securities available for sale
Investment securities available for sale	$ 1,904,255	$ 1,886,395
Equity Securities [Member]
Securities available for sale
Investment securities available for sale	414	0
U S Treasury Securities [Member]
Securities available for sale
Investment securities available for sale	7,518	7,497
Us Government Agencies Debt Securities Noncallable [Member]
Securities available for sale
Investment securities available for sale	335,572	315,467
Us Government Agencies Debt Securities Callable [Member]
Securities available for sale
Investment securities available for sale	1,509,609	1,509,807
US States And Political Subdivisions Member [Member]
Securities available for sale
Investment securities available for sale	26,448	28,217
Private Label Mbs [Member]
Securities available for sale
Investment securities available for sale	24,594	25,307
Interest Rate Cap [Member] | Purchase
Derivatives, included in assets:
Derivatives, included in assets	368	806
Interest Rate Cap [Member] | Written
Derivatives, included in liabilities:
Derivatives, included in liabilities	364	798
Forward And Future Contracts [Member]
Derivatives, included in liabilities:
Derivatives, included in liabilities	272	123
Other Available For Sale Securities [Member]
Securities available for sale
Investment securities available for sale	100	100
Fair Value Inputs Level 1 [Member] | Equity Securities [Member]
Securities available for sale
Investment securities available for sale	414	0
Fair Value Inputs Level 1 [Member] | U S Treasury Securities [Member]
Securities available for sale
Investment securities available for sale	7,518	7,497
Fair Value Inputs Level 1 [Member] | Us Government Agencies Debt Securities Noncallable [Member]
Securities available for sale
Investment securities available for sale	0	0
Fair Value Inputs Level 1 [Member] | Us Government Agencies Debt Securities Callable [Member]
Securities available for sale
Investment securities available for sale	0	0
Fair Value Inputs Level 1 [Member] | US States And Political Subdivisions Member [Member]
Securities available for sale
Investment securities available for sale	0	0
Fair Value Inputs Level 1 [Member] | Private Label Mbs [Member]
Securities available for sale
Investment securities available for sale	0	0
Fair Value Inputs Level 1 [Member] | Interest Rate Cap [Member] | Purchase
Derivatives, included in assets:
Derivatives, included in assets	0	0
Fair Value Inputs Level 1 [Member] | Interest Rate Cap [Member] | Written
Derivatives, included in liabilities:
Derivatives, included in liabilities	0	0
Fair Value Inputs Level 1 [Member] | Forward And Future Contracts [Member]
Derivatives, included in liabilities:
Derivatives, included in liabilities		0
Fair Value Inputs Level 1 [Member] | Interest Rate Swap [Member]
Derivatives, included in liabilities:
Derivatives, included in liabilities	0
Fair Value Inputs Level 1 [Member] | Other Available For Sale Securities [Member]
Securities available for sale
Investment securities available for sale	0	0
Fair Value Inputs Level 2 [Member] | Equity Securities [Member]
Securities available for sale
Investment securities available for sale	0	0
Fair Value Inputs Level 2 [Member] | U S Treasury Securities [Member]
Securities available for sale
Investment securities available for sale	0	0
Fair Value Inputs Level 2 [Member] | Us Government Agencies Debt Securities Noncallable [Member]
Securities available for sale
Investment securities available for sale	335,572	315,467
Fair Value Inputs Level 2 [Member] | Us Government Agencies Debt Securities Callable [Member]
Securities available for sale
Investment securities available for sale	1,509,609	1,509,807
Fair Value Inputs Level 2 [Member] | US States And Political Subdivisions Member [Member]
Securities available for sale
Investment securities available for sale	24,479	26,327
Fair Value Inputs Level 2 [Member] | Private Label Mbs [Member]
Securities available for sale
Investment securities available for sale	0	0
Fair Value Inputs Level 2 [Member] | Interest Rate Cap [Member] | Purchase
Derivatives, included in assets:
Derivatives, included in assets	368	806
Fair Value Inputs Level 2 [Member] | Interest Rate Cap [Member] | Written
Derivatives, included in liabilities:
Derivatives, included in liabilities	364	798
Fair Value Inputs Level 2 [Member] | Forward And Future Contracts [Member]
Derivatives, included in liabilities:
Derivatives, included in liabilities	272	123
Fair Value Inputs Level 2 [Member] | Other Available For Sale Securities [Member]
Securities available for sale
Investment securities available for sale	0	0
Fair Value Inputs Level 3 [Member] | Equity Securities [Member]
Securities available for sale
Investment securities available for sale	0	0
Fair Value Inputs Level 3 [Member] | U S Treasury Securities [Member]
Securities available for sale
Investment securities available for sale	0	0
Fair Value Inputs Level 3 [Member] | Us Government Agencies Debt Securities Noncallable [Member]
Securities available for sale
Investment securities available for sale	0	0
Fair Value Inputs Level 3 [Member] | Us Government Agencies Debt Securities Callable [Member]
Securities available for sale
Investment securities available for sale	0	0
Fair Value Inputs Level 3 [Member] | US States And Political Subdivisions Member [Member]
Securities available for sale
Investment securities available for sale	1,969	1,890
Fair Value Inputs Level 3 [Member] | Private Label Mbs [Member]
Securities available for sale
Investment securities available for sale	24,594	25,307
Fair Value Inputs Level 3 [Member] | Interest Rate Cap [Member] | Purchase
Derivatives, included in assets:
Derivatives, included in assets	0	0
Fair Value Inputs Level 3 [Member] | Interest Rate Cap [Member] | Written
Derivatives, included in liabilities:
Derivatives, included in liabilities	0	0
Fair Value Inputs Level 3 [Member] | Forward And Future Contracts [Member]
Derivatives, included in liabilities:
Derivatives, included in liabilities	0	0
Fair Value Inputs Level 3 [Member] | Other Available For Sale Securities [Member]
Securities available for sale
Investment securities available for sale	$ 100	$ 100