5. INVESTMENT SECURITIES - Amortized cost and estimated fair value of investment securities contractual maturity (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014
Amortized Cost
Net Investment Income [Line Items]
Within one year	$ 175
After one year through five years	3,809
After five years through ten years	11,890
After ten years	10,516
Investment securities not due at a single maturity date:
Investment securities not due at a single maturity date: Available-for-Sale	283,446
Investment securities not due at a single maturity date: Held-to-Maturity	862
Amortized Cost | US Government Agencies and Sponsored Agencies
Investment securities not due at a single maturity date:
Investment securities not due at a single maturity date: Available-for-Sale	257,002
Investment securities not due at a single maturity date: Held-to-Maturity	862
Amortized Cost | Corporate stock
Investment securities not due at a single maturity date:
Investment securities not due at a single maturity date: Available-for-Sale	54
Investment securities not due at a single maturity date: Held-to-Maturity
Estimated Fair Value
Net Investment Income [Line Items]
Within one year	176
After one year through five years	3,984
After five years through ten years	12,608
After ten years	11,104
Investment securities not due at a single maturity date:
Investment securities not due at a single maturity date: Available-for-Sale	289,064
Investment securities not due at a single maturity date: Held-to-Maturity	922
Estimated Fair Value | US Government Agencies and Sponsored Agencies
Investment securities not due at a single maturity date:
Investment securities not due at a single maturity date: Available-for-Sale	261,115
Investment securities not due at a single maturity date: Held-to-Maturity	922
Estimated Fair Value | Corporate stock
Investment securities not due at a single maturity date:
Investment securities not due at a single maturity date: Available-for-Sale	77
Investment securities not due at a single maturity date: Held-to-Maturity