STOCKHOLDERS' EQUITY (Details 6) (USD $) In Thousands, unless otherwise specified	3 Months Ended		12 Months Ended
	Mar. 31, 2012	Mar. 31, 2011	Dec. 31, 2011
Unrealized gain on investment securities available-for-sale:
Unrealized gains on holding gains arising during period, before-tax amount	$ 28,640	$ 4,022
Less: reclassification adjustment for losses/(gains) included in income, before-tax amount	5,826	6,225
Net unrealized gains, before-tax amount	34,466	10,247
Noncredit-related impairment loss on securities, before tax	(5,066)	(5,091)	(5,100)
Foreign currency translation adjustments, before-tax amount	17	(1,262)
Other comprehensive income, before-tax amount	29,417	3,894
Unrealized gain on investment securities available-for-sale:
Unrealized gains on holding gains arising during period, tax (expense) or benefit	(12,029)	(1,689)
Less: reclassification adjustment for losses/(gains) included in income, tax (expense) or benefit	(2,447)	(2,614)
Net unrealized gains, tax (expense) or benefit	(14,476)	(4,303)
Noncredit-related impairment loss on securities, tax effect	(2,128)	(2,138)
Foreign currency translation adjustments, tax (expense) or benefit	(7)	530
Other comprehensive income, tax (expense) or benefit	(12,355)	(1,635)
Unrealized gain on investment securities available-for-sale:
Unrealized gains on holding gains arising during period, net of tax amount	16,611	2,333
Less: reclassification adjustment for losses/(gains) included in income	3,379	3,611
Net unrealized gains, net of tax amount	19,990	5,944
Noncredit-related impairment loss on securities, net of tax amount	(2,938)	(2,953)
Foreign currency translation adjustments, net of tax amount	10	(732)
Other comprehensive income	$ 17,062	$ 2,259