ACCUMULATED OTHER COMPREHENSIVE INCOME - Reclassifications out 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]
Net realized investment gains (losses)	$ (390)		$ 1,007	$ 3,215		$ 3,850
Income tax expense (benefit), current	1,452		(3,875)	(2,848)		(11,973)
Total reclassification adjustment	786	[1]		4,788	[1]
Unrealized Gains and (Losses) on Available-for-sale securities | Reclassification Out Of Accumulated Other Comprehensive Income [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Net realized investment gains (losses)	527	[1]		5,320	[1]
Income tax expense (benefit), current	(184)	[1]		(1,862)	[1]
Total reclassification adjustment	343	[1]		3,458	[1]
Unrecognized pension and postretirement benefit obligations | Reclassification Out Of Accumulated Other Comprehensive Income [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Net actuarial loss	(144)	[1],[2]		(433)	[1],[2]
Prior service credit	826	[1],[2]		2,480	[1],[2]
Total before tax	682	[1]		2,047	[1]
Income tax expense (benefit), current	(239)	[1]		(717)	[1]
Total reclassification adjustment	$ 443	[1]		$ 1,330	[1]

[1] Amounts in parentheses indicate debits to net income

[2] These accumulated other comprehensive income components are included in the computation of net periodic pension and postretirement benefit cost (income) (see Note 6, Employee Retirement Plans, for additional details).