SCHEDULE III-SUPPLEMENTARY INSURANCE INFORMATION (Details) - 10K (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Supplementary insurance information
Deferred policy acquisition costs	$ 65,123	$ 61,508	$ 52,344
Unpaid losses and settlement expenses, gross	1,121,040	1,129,433	1,158,483
Unearned premiums, gross	401,412	392,081	369,346
Net premiums earned	687,375	630,802	576,571
Incurred losses and settlement expenses
Current accident year	361,451	332,282	336,228
Prior accident years	(64,842)	(72,481)	(64,583)
Policy acquisition costs	229,283	210,651	196,362
Other operating expenses	54,464	53,557	44,971
Net premiums written	703,152	666,322	593,086
Casualty segment
Supplementary insurance information
Deferred policy acquisition costs	31,334	28,553	19,673
Unpaid losses and settlement expenses, gross	964,699	947,677	955,730
Unearned premiums, gross	237,117	228,907	199,672
Net premiums earned	382,105	324,022	267,697
Incurred losses and settlement expenses
Current accident year	251,958	210,665	184,555
Prior accident years	(52,825)	(61,805)	(40,449)
Policy acquisition costs	108,747	93,463	76,765
Other operating expenses	28,284	26,107	21,387
Net premiums written	395,853	362,459	284,058
Property segment
Supplementary insurance information
Deferred policy acquisition costs	13,827	14,275	14,523
Unpaid losses and settlement expenses, gross	120,858	146,122	169,250
Unearned premiums, gross	94,092	97,116	103,854
Net premiums earned	197,776	200,141	202,402
Incurred losses and settlement expenses
Current accident year	90,712	103,544	132,507
Prior accident years	(1,123)	(7,273)	(16,800)
Policy acquisition costs	58,646	58,650	60,070
Other operating expenses	16,623	17,616	14,933
Net premiums written	195,580	196,467	202,971
Surety segment
Supplementary insurance information
Deferred policy acquisition costs	19,962	18,680	18,148
Unpaid losses and settlement expenses, gross	35,483	35,634	33,503
Unearned premiums, gross	70,203	66,058	65,820
Net premiums earned	107,494	106,639	106,472
Incurred losses and settlement expenses
Current accident year	18,781	18,073	19,166
Prior accident years	(10,894)	(3,403)	(7,334)
Policy acquisition costs	61,890	58,538	59,527
Other operating expenses	9,557	9,834	8,651
Net premiums written	$ 111,719	$ 107,396	$ 106,057