ACCUMULATED OTHER COMPREHENSIVE INCOME - Reclassifications out of Accumulated Other Comprehensive Income (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended			6 Months Ended
	Jun. 30, 2014		Jun. 30, 2013	Jun. 30, 2014		Jun. 30, 2013
Accumulated Other Comprehensive Income Loss [Line Items]
Net realized investment gains (losses)	$ 2,343		$ 175	$ 3,605		$ 2,843
Income tax expense (benefit), current	(198)		(2,602)	(4,300)		(8,098)
Total reclassification adjustment	2,494	[1]		4,002	[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)	3,163	[1]		4,793	[1]
Income tax expense (benefit), current	(1,107)	[1]		(1,678)	[1]
Total reclassification adjustment	2,056	[1]		3,115	[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	(153)	[1],[2]		(289)	[1],[2]
Prior service credit	827	[1],[2]		1,654	[1],[2]
Total before tax	674	[1]		1,365	[1]
Income tax expense (benefit), current	(236)	[1]		(478)	[1]
Total reclassification adjustment	$ 438	[1]		$ 887	[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).