COMPREHENSIVE INCOME (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013		Jun. 30, 2012
Before Tax Amount [Abstract]
Other comprehensive (loss) income, before tax	$ (42,476)	$ 9,419	$ (49,729)		$ 5,831
Tax Effect [Abstract]
Other comprehensive (loss) income, tax effect	16,263	(3,949)	19,042		(2,236)
Net of Tax Amount [Abstract]
Other comprehensive (loss) income, net of tax	(26,213)	5,470	(30,687)		3,595
Net income (loss)	20,755	20,624	41,560		43,490
Comprehensive income (loss)	(5,458)	26,094	10,873		47,085
Accumulated Net Unrealized Investment Gain (Loss) [Member]
Before Tax Amount [Abstract]
Other comprehensive loss before reclassifications, before tax	(43,810)	8,404	(52,381)		3,698
Tax Effect [Abstract]
Unrealized losses arising during holding period, tax effect	16,773	(3,219)	20,056		(1,420)
Net of Tax Amount [Abstract]
Other Comprehensive Loss Before Reclassification Adjustments, Net Of Tax	(27,037)	5,185	(32,325)		2,278
Accumulated Net Unrealized Investment Gain (Loss) [Member] | Amounts reclassified from accumulated other comprehensive income [Member]
Before Tax Amount [Abstract]
Amounts reclassified from accumulated OCI, before tax	(3)	(177)	(22)	[1]	(251)	[1]
Tax Effect [Abstract]
Reclassification adjustment for net gains realized in net income, tax effect	1	68	8	[1]	96	[1]
Net of Tax Amount [Abstract]
Amounts reclassified from accumulated OCI, net of tax	(2)	(109)	(14)	[1]	(155)	[1]
Accumulated Defined Benefit Plans Adjustment [Member]
Before Tax Amount [Abstract]
Other comprehensive loss before reclassifications, before tax	1,337	1,192	2,674	[2]	2,384	[2]
Tax Effect [Abstract]
Recognized employee benefit plan net periodic benefit cost, tax effect	(511)	(798)	(1,022)	[2]	(912)	[2]
Net of Tax Amount [Abstract]
Other Comprehensive Loss Before Reclassification Adjustments, Net Of Tax	$ 826	$ 394	$ 1,652	[2]	$ 1,472	[2]

[1] Reclassification adjustments for net gains on available-for-sale securities are reported as net security gains on the consolidated statements of income.

[2] Recognized employee benefit plan net periodic benefit cost include amortization of unrecognized transition amount, recognized prior service cost and recognized net loss. For more information, see Note 9 - Pension Benefits.