SCHEDULE II-CONDENSED FINANCIAL INFORMATION OF REGISTRANT (PARENT COMPANY) - Balance Sheets (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
ASSETS
Cash	$ 11,081	$ 30,620	$ 39,469	$ 44,314
Short-term investments, at cost which approximates fair value	6,262	16,339
Investments in unconsolidated investee, at equity value	70,784	60,046
Fixed income:
Available-for-sale, at fair value (amortized cost - $45,178 in 2015 and $46,226 in 2014)	1,538,110	1,495,087
Property and equipment, at cost, net of accumulated depreciation of $765 in 2015 and $528 in 2014	47,102	42,549
TOTAL ASSETS	2,736,579	2,775,542
Liabilities:
Bonds payable, long-term debt	149,668	149,625
TOTAL LIABILITIES	1,913,110	1,930,480
Shareholders' Equity
Common stock ($1 par value, authorized 100,000,000 shares, issued 66,474,342 shares in 2015 and 66,032,929 shares in 2014, and outstanding 43,544,128 shares in 2015 and 43,102,715 shares in 2014)	66,474	66,033
Paid-in capital	221,345	213,737
Accumulated other comprehensive earnings	123,774	171,383
Retained earnings	804,875	786,908
Deferred compensation	10,647	13,769
Treasury shares at cost (22,930,214 shares in 2015 and 2014)	(403,646)	(406,768)
TOTAL SHAREHOLDERS’ EQUITY	823,469	845,062	828,966	796,363
TOTAL LIABILITIES AND SHAREHOLDERS’ EQUITY	2,736,579	2,775,542
PARENT COMPANY
ASSETS
Cash	178	374	$ 181	$ 14,023
Short-term investments, at cost which approximates fair value	86	177
Accounts receivable, affiliates		3,803
Investments in subsidiaries, at equity value	881,950	903,738
Investments in unconsolidated investee, at equity value	62,650	54,316
Fixed income:
Available-for-sale, at fair value (amortized cost - $45,178 in 2015 and $46,226 in 2014)	44,889	46,136
Property and equipment, at cost, net of accumulated depreciation of $765 in 2015 and $528 in 2014	2,971	3,208
Income taxes receivable - current	1,195	463
Deferred debt costs	1,114	1,258
Other assets	608	681
TOTAL ASSETS	995,641	1,014,154
Liabilities:
Accounts payable, affiliates	408
Income taxes payable--deferred	19,254	16,372
Bonds payable, long-term debt	149,668	149,625
Interest payable, long-term debt	2,153	2,153
Other liabilities	689	942
TOTAL LIABILITIES	172,172	169,092
Shareholders' Equity
Common stock ($1 par value, authorized 100,000,000 shares, issued 66,474,342 shares in 2015 and 66,032,929 shares in 2014, and outstanding 43,544,128 shares in 2015 and 43,102,715 shares in 2014)	66,474	66,033
Paid-in capital	221,345	213,737
Accumulated other comprehensive earnings	123,774	171,383
Retained earnings	804,875	786,908
Deferred compensation	10,647	13,769
Treasury shares at cost (22,930,214 shares in 2015 and 2014)	(403,646)	(406,768)
TOTAL SHAREHOLDERS’ EQUITY	823,469	845,062
TOTAL LIABILITIES AND SHAREHOLDERS’ EQUITY	$ 995,641	$ 1,014,154