COMPREHENSIVE INCOME (Details) (USD $) In Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010
Net unrealized gains on available-for-sale securities, before tax amount [Abstract]
Unrealized gains arising during holding period, before tax amount	$ 46,461	$ 7,889	$ 42,417	$ 4,931
Less: Reclassification adjustment for net gains realized in net income, before tax amount	(10,045)	585	(10,062)	(712)
Recognized employee benefit plan net periodic benefit cost, before tax amount	633	652	1,266	1,286
Other comprehensive income (loss), before tax amount	37,049	9,126	33,621	5,505
Net unrealized gains on available-for-sale securities, tax (expense) benefit [Abstract]
Unrealized losses arising during holding period, tax (expense) benefit	(17,781)	(3,015)	(16,244)	(1,884)
Less: Reclassification adjustment for net gains realized in net income, tax (expense) benefit	3,842	(224)	3,849	272
Recognized employee benefit plan net periodic benefit cost, tax (expense) benefit	(242)	(250)	(484)	(492)
Other comprehensive income (loss), tax (expense) benefit	(14,181)	(3,489)	(12,879)	(2,104)
Net unrealized gains on available-for-sale securities, net of tax amount [Abstract]
Unrealized losses arising during holding periods, net of tax amount	28,680	4,874	26,173	3,047
Less: Reclassification adjustment for net gains realized in net income, net of tax amount	(6,203)	361	(6,213)	(440)
Recognized employee benefit plan net periodic benefit cost, net of tax amount	391	402	782	794
Other comprehensive income (loss), net of tax amount	22,868	5,637	20,742	3,401
Net income (loss)	12,826	(12,560)	12,332	(4,164)
Comprehensive income (loss)	$ 35,694	$ (6,923)	$ 33,074	$ (763)