COMPREHENSIVE INCOME (Details) (USD $) In Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010
Net unrealized gains on available-for- sale securities, before tax amount [Abstract]
Unrealized gains arising during holding period, before tax amount	$ 14,563	$ 5,421	$ 56,981	$ 10,351
Less: Reclassification adjustment for net gains realized in net income, before tax amount	(2,047)	(2,327)	(12,109)	(3,039)
Recognized employee benefit plan net periodic benefit cost, before tax amount	947	645	2,213	1,931
Other comprehensive income, before tax amount	13,463	3,739	47,085	9,243
Net unrealized gains on available-for- sale securities, tax (expense) benefit [Abstract]
Unrealized gains arising during holding period, tax (expense) benefit	(5,578)	(2,078)	(21,823)	(3,962)
Less: Reclassification adjustment for net gains realized in net income, tax (expense) benefit	783	890	4,632	1,162
Recognized employee benefit plan net periodic benefit cost, tax (expense) benefit	(362)	(247)	(846)	(739)
Other comprehensive income, tax (expense) benefit	(5,157)	(1,435)	(18,037)	(3,539)
Net unrealized gains on available-for- sale securities, net of tax amount [Abstract]
Unrealized gains arising during holding period, net of tax amount	8,985	3,343	35,158	6,389
Less: Reclassification adjustment for net gains realized in net income, net of tax amount	(1,264)	(1,437)	(7,477)	(1,877)
Recognized employee benefit plan net periodic benefit cost, net of tax amount	585	398	1,367	1,192
Other comprehensive income, net of tax amount	8,306	2,304	29,048	5,704
Net income	11,934	11,260	24,266	7,096
Comprehensive income	$ 20,240	$ 13,564	$ 53,314	$ 12,800