SCHEDULE I -- SUMMARY OF INVESTMENTS-OTHER THAN INVESTMENTS IN RELATED PARTIES (Details) - USD ($) $ in Thousands		Dec. 31, 2017	Dec. 31, 2016
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost		$ 521,017	$ 494,561
Amount at which shown in the balance sheet		693
Investments classified as cash and cash equivalents		59,174
Total Investments [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost		652,768
Fair value		724,616
Amount at which shown in the balance sheet	[1]	724,616
Bonds [Member] | Total Fixed Maturities [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost		521,017
Fair value		521,853
Amount at which shown in the balance sheet	[1]	521,853
Bonds [Member] | Agency Collateralized Mortgage Obligations [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost		15,839
Fair value		16,586
Amount at which shown in the balance sheet	[1]	16,586
Bonds [Member] | Agency Mortgage-backed Securities [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost		27,180
Fair value		27,075
Amount at which shown in the balance sheet	[1]	27,075
Bonds [Member] | Asset-backed Securities [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost		42,861
Fair value		43,469
Amount at which shown in the balance sheet	[1]	43,469
Bonds [Member] | Bank Loans [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost		19,271
Fair value		19,488
Amount at which shown in the balance sheet	[1]	19,488
Bonds [Member] | Certificates of Deposit [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost		3,124
Fair value		3,135
Amount at which shown in the balance sheet	[1]	3,135
Bonds [Member] | Collateralized Mortgage Obligations [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost		6,079
Fair value		6,492
Amount at which shown in the balance sheet	[1]	6,492
Bonds [Member] | Corporate Securities [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost		197,201
Fair value		197,130
Amount at which shown in the balance sheet	[1]	197,130
Bonds [Member] | Mortgage-backed Securities [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost		23,656
Fair value		24,204
Amount at which shown in the balance sheet	[1]	24,204
Bonds [Member] | Municipal Obligations [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost		97,059
Fair value		96,650
Amount at which shown in the balance sheet	[1]	96,650
Bonds [Member] | Non-U.S. Government Obligations [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost		39,189
Fair value		38,613
Amount at which shown in the balance sheet	[1]	38,613
Bonds [Member] | U.S. Government Obligations [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost		49,558
Fair value		49,011
Amount at which shown in the balance sheet	[1]	49,011
Common Stocks [Member] | Total Equity Securities [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost		130,751
Fair value		201,763
Amount at which shown in the balance sheet	[1]	201,763
Common Stocks [Member] | Consumer [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost		23,565
Fair value		46,578
Amount at which shown in the balance sheet	[1]	46,578
Common Stocks [Member] | Energy [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost		6,763
Fair value		10,278
Amount at which shown in the balance sheet	[1]	10,278
Common Stocks [Member] | Financial [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost		31,859
Fair value		45,470
Amount at which shown in the balance sheet	[1]	45,470
Common Stocks [Member] | Industrial [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost		8,949
Fair value		25,402
Amount at which shown in the balance sheet	[1]	25,402
Common Stocks [Member] | Technology [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost		5,768
Fair value		13,061
Amount at which shown in the balance sheet	[1]	13,061
Common Stocks [Member] | Funds (e.g. mutual funds, closed end funds, ETFs) [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost		46,177
Fair value		50,291
Amount at which shown in the balance sheet	[1]	50,291
Common Stocks [Member] | Other [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost		7,670
Fair value		10,683
Amount at which shown in the balance sheet	[1]	10,683
Short-term [Member] | Total Short-term and Other [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost		1,000
Fair value		1,000
Amount at which shown in the balance sheet	[1]	1,000
Short-term [Member] | Certificates of Deposit [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost		1,000
Fair value		1,000
Amount at which shown in the balance sheet	[1]	$ 1,000

[1] Amounts presented above do not include investments of $59,174 classified as cash and cash equivalents in the balance sheet.