STOCKHOLDERS' EQUITY AND EARNINGS PER SHARE (Details 5) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2015		Mar. 31, 2014
Unrealized gains on available-for-sale investment securities:
Net unrealized gains arising during period, before-tax amount	$ 20,482		$ 26,590
Less: reclassification adjustment for gains included in net income, before-tax amount	(4,404)	[1]	(3,418)	[1]
Net unrealized gains, before-tax amount	16,078		23,172
Unrealized losses on other investments:
Net unrealized losses arising during period, before-tax amount	(12)		(29)
Net unrealized losses, before-tax amount	(12)		(29)
Other comprehensive income, before-tax amount	16,066		23,143
Unrealized gains on available-for-sale investment securities:
Net unrealized gains arising during period, tax expense or benefit	(8,603)		(11,168)
Less: reclassification adjustment for gains included in net income, tax expense or benefit	1,850	[1]	1,435	[1]
Net unrealized gains, tax expense or benefit	(6,753)		(9,733)
Unrealized losses on other investments:
Net unrealized losses arising during period, tax expense or benefit	5		12
Net unrealized losses, tax expense or benefit	5		12
Other comprehensive income, tax expense or benefit	(6,748)		(9,721)
Unrealized gains on available-for-sale investment securities:
Net unrealized gains arising during period, net-of-tax amount	11,879		15,422
Less: reclassification adjustment for gains included in net income, net-of-tax amount	(2,554)	[1]	(1,983)	[1]
Net unrealized gains, net-of-tax amount	9,325		13,439
Unrealized losses on other investments:
Net unrealized losses arising during period, net-of-tax amount	(7)		(17)
Net unrealized losses, net-of-tax amount	(7)		(17)
Other comprehensive income	$ 9,318		$ 13,422

[1] The pretax amount is reported in net gains on sales of available-for-sale investment securities in the consolidated statements of income.