SCHEDULE II-CONDENSED FINANCIAL INFORMATION OF REGISTRANT (PARENT COMPANY) - Balance Sheets (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
ASSETS
Cash	$ 18,269	$ 11,081	$ 30,620	$ 39,469
Short-term investments, at cost which approximates fair value	5,015	6,262
Investments in unconsolidated investee, at equity value	72,240	70,784
Fixed income:
Available-for-sale, at fair value (amortized cost - $45,901 in 2016 and $45,178 in 2015)	1,605,209	1,538,110
Property and equipment, at cost, net of accumulated depreciation of $1,523 in 2016 and $765 in 2015	54,606	47,102
TOTAL ASSETS	2,777,633	2,735,465
Liabilities:
Bonds payable, long-term debt	148,741	148,554
TOTAL LIABILITIES	1,954,061	1,911,996
Shareholders' Equity
Common stock ($1 par value, authorized 100,000,000 shares, issued 66,874,911 shares in 2016 and 66,474,342 shares in 2015, and outstanding 43,944,697 shares in 2016 and 43,544,128 shares in 2015)	66,875	66,474
Paid-in capital	229,779	221,345
Accumulated other comprehensive earnings	122,610	123,774
Retained earnings	797,307	804,875
Deferred compensation	11,496	10,647
Treasury shares at cost (22,930,214 shares in 2016 and 2015)	(404,495)	(403,646)
TOTAL SHAREHOLDERS’ EQUITY	823,572	823,469	845,062	828,966
TOTAL LIABILITIES AND SHAREHOLDERS’ EQUITY	2,777,633	2,735,465
PARENT COMPANY
ASSETS
Cash	21	178	$ 374	$ 181
Short-term investments, at cost which approximates fair value	23	86
Accounts receivable, affiliates	127
Investments in subsidiaries, at equity value	882,095	881,950
Investments in unconsolidated investee, at equity value	62,604	62,650
Fixed income:
Available-for-sale, at fair value (amortized cost - $45,901 in 2016 and $45,178 in 2015)	45,885	44,889
Property and equipment, at cost, net of accumulated depreciation of $1,523 in 2016 and $765 in 2015	2,213	2,971
Income taxes receivable - current	858	1,195
Other assets	329	608
TOTAL ASSETS	994,155	994,527
Liabilities:
Accounts payable, affiliates		408
Income taxes payable--deferred	19,145	19,254
Bonds payable, long-term debt	148,741	148,554
Interest payable, long-term debt	2,153	2,153
Other liabilities	544	689
TOTAL LIABILITIES	170,583	171,058
Shareholders' Equity
Common stock ($1 par value, authorized 100,000,000 shares, issued 66,874,911 shares in 2016 and 66,474,342 shares in 2015, and outstanding 43,944,697 shares in 2016 and 43,544,128 shares in 2015)	66,875	66,474
Paid-in capital	229,779	221,345
Accumulated other comprehensive earnings	122,610	123,774
Retained earnings	797,307	804,875
Deferred compensation	11,496	10,647
Treasury shares at cost (22,930,214 shares in 2016 and 2015)	(404,495)	(403,646)
TOTAL SHAREHOLDERS’ EQUITY	823,572	823,469
TOTAL LIABILITIES AND SHAREHOLDERS’ EQUITY	$ 994,155	$ 994,527