DERIVATIVES - Summary of Derivative Financial Instruments and Balances (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
Derivatives, Fair Value [Line Items]
Notional Amount	$ 890,200	$ 775,328
Estimate Fair Value Gain	25,813	24,566
Estimate Fair Value Loss	(29,015)	(28,123)
Pay fixed interest rate swaps with counterparty
Derivatives, Fair Value [Line Items]
Notional Amount	16,932
Fair Value Hedges
Derivatives, Fair Value [Line Items]
Notional Amount	890,200	775,328
Fair Value Hedges | Pay fixed interest rate swaps with counterparty | Accrued interest and other liabilities
Derivatives, Fair Value [Line Items]
Notional Amount	16,932	17,456
Estimate Fair Value Gain	0	0
Estimate Fair Value Loss	(2,079)	(2,263)
Fair Value Hedges | Matched interest rate swaps | Accrued interest and other liabilities
Derivatives, Fair Value [Line Items]
Notional Amount	436,634	378,936
Estimate Fair Value Gain	0	0
Estimate Fair Value Loss	(26,936)	(25,860)
Fair Value Hedges | Matched interest rate swaps | Accrued interest and other assets
Derivatives, Fair Value [Line Items]
Notional Amount	436,634	378,936
Estimate Fair Value Gain	25,813	24,566
Estimate Fair Value Loss	$ 0	$ 0