SUMMARY OF INVESTMENTS (Net Investment Income) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Other	$ 1,227	$ 1,452	$ 1,998
Total investment income	114,525	107,818	110,925
Less investment expenses	7,703	7,037	6,316
Net investment income	106,822	100,781	104,609
Fixed Maturities
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Interest income	92,362	92,777	97,969
Equity securities
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Dividends on equity securities	7,050	7,208	6,602
Other long-term investments
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Interest income	2,394	2,567	1,927
Other long-term investments | Change in Value
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Other	10,742	3,266	1,917
Mortgage Loans
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Interest income	221	237	252
Short-term investments
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Interest income	84	6	5
Cash and cash equivalents
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Interest income	$ 445	$ 305	$ 255