ACCUMULATED OTHER COMPREHENSIVE INCOME - Components of Accumulated Other Comprehensive Income (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended			9 Months Ended
	Sep. 30, 2014		Sep. 30, 2013	Sep. 30, 2014		Sep. 30, 2013
Accumulated Other Comprehensive Income Loss [Line Items]
Balance at December 31, 2013				$ 59,010	[1]
Other comprehensive income (loss) before reclassifications				24,007	[1]
Amounts reclassified from accumulated other comprehensive income				(4,788)	[1]
Other comprehensive income (loss)	(990)		(630)	19,219	[1]	(18,875)
Balance at September 30, 2014	78,229	[1]		78,229	[1]
Unrealized Gains and (Losses) on Available-for-sale securities
Accumulated Other Comprehensive Income Loss [Line Items]
Balance at December 31, 2013				48,376	[1]
Other comprehensive income (loss) before reclassifications				24,007	[1]
Amounts reclassified from accumulated other comprehensive income				(3,458)	[1]
Other comprehensive income (loss)				20,549	[1]
Balance at September 30, 2014	68,925	[1]		68,925	[1]
Unrecognized pension and postretirement benefit obligations
Accumulated Other Comprehensive Income Loss [Line Items]
Balance at December 31, 2013				10,634	[1]
Other comprehensive income (loss) before reclassifications				0	[1]
Amounts reclassified from accumulated other comprehensive income				(1,330)	[1]
Other comprehensive income (loss)				(1,330)	[1]
Balance at September 30, 2014	$ 9,304	[1]		$ 9,304	[1]

[1] All amounts are net of tax. Amounts in parentheses indicate debits.