Fair Value (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Fixed maturities [Abstract]
Total fixed maturities	$ 489,606	$ 491,904
Equity securities [Abstract]
Total equity securities	194,167	119,945
Recurring [Member]
Fixed maturities [Abstract]
Agency collateralized mortgage obligations	11,017	6,171
Agency mortgage-backed securities	19,712	4,770
Asset-backed securities	50,030	45,183
Bank loans	24,986	10,349
Certificates of deposit	3,138	3,117
Collateralized mortgage obligations	7,055	9,104
Corporate securities	160,716	137,932
Options embedded in convertible securities	5,078	4,751
Mortgage-backed securities	20,643	24,571
Municipal obligations	102,805	129,335
Non-U.S. government obligations	32,942	24,681
U.S. government obligations	51,484	91,940
Total fixed maturities	489,606	491,904
Equity securities [Abstract]
Consumer	41,912	32,576
Energy	8,168	12,842
Financial	46,167	31,186
Industrial	23,971	21,145
Technology	11,826	8,858
Mutual fund	53,528	6,995
Other	8,595	6,343
Total equity securities	194,167	119,945
Short-term	1,000	1,500
Cash equivalents	64,153	59,683
Total fair value	748,926	673,032
Recurring [Member] | Level 1 [Member]
Fixed maturities [Abstract]
Agency collateralized mortgage obligations	0	0
Agency mortgage-backed securities	0	0
Asset-backed securities	0	0
Bank loans	0	0
Certificates of deposit	3,138	3,117
Collateralized mortgage obligations	0	0
Corporate securities	0	0
Options embedded in convertible securities	0	0
Mortgage-backed securities	0	0
Municipal obligations	0	0
Non-U.S. government obligations	0	0
U.S. government obligations	0	0
Total fixed maturities	3,138	3,117
Equity securities [Abstract]
Consumer	41,912	32,576
Energy	8,168	12,842
Financial	46,167	30,943
Industrial	23,971	20,262
Technology	11,826	8,858
Mutual fund	53,528	0
Other	8,595	6,343
Total equity securities	194,167	111,824
Short-term	1,000	1,500
Cash equivalents	0	0
Total fair value	198,305	116,441
Recurring [Member] | Level 2 [Member]
Fixed maturities [Abstract]
Agency collateralized mortgage obligations	11,017	6,171
Agency mortgage-backed securities	19,712	4,770
Asset-backed securities	50,030	37,919
Bank loans	24,986	0
Certificates of deposit	0	0
Collateralized mortgage obligations	7,055	6,409
Corporate securities	160,558	135,794
Options embedded in convertible securities	5,078	4,751
Mortgage-backed securities	20,413	22,206
Municipal obligations	102,805	129,190
Non-U.S. government obligations	32,942	24,419
U.S. government obligations	51,484	91,940
Total fixed maturities	486,080	463,569
Equity securities [Abstract]
Consumer	0	0
Energy	0	0
Financial	0	243
Industrial	0	883
Technology	0	0
Mutual fund	0	6,995
Other	0	0
Total equity securities	0	8,121
Short-term	0	0
Cash equivalents	64,153	59,683
Total fair value	550,233	531,373
Recurring [Member] | Level 3 [Member]
Fixed maturities [Abstract]
Agency collateralized mortgage obligations	0	0
Agency mortgage-backed securities	0	0
Asset-backed securities	0	7,264
Bank loans	0	10,349
Certificates of deposit	0	0
Collateralized mortgage obligations	0	2,695
Corporate securities	158	2,138
Options embedded in convertible securities	0	0
Mortgage-backed securities	230	2,365
Municipal obligations	0	145
Non-U.S. government obligations	0	262
U.S. government obligations	0	0
Total fixed maturities	388	25,218
Equity securities [Abstract]
Consumer	0	0
Energy	0	0
Financial	0	0
Industrial	0	0
Technology	0	0
Mutual fund	0	0
Other	0	0
Total equity securities	0	0
Short-term	0	0
Cash equivalents	0	0
Total fair value	$ 388	$ 25,218