Reinsurance (Ceded Reinsurance Receivable Assets) (Details) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2016	Dec. 31, 2015
Ceded Credit Risk [Line Items]
Reinsurance ceded receivables	$ 694,906	$ 637,859
Reinsurance Recoverables, Percentage of Total	100.00%	100.00%
Other Reinsurers [Member]
Ceded Credit Risk [Line Items]
Reinsurance ceded receivables	$ 121,278	$ 107,077
Reinsurance Recoverables, Percentage of Total	17.50%	16.80%
AM Best, A+ Rating [Member] | Reinsurer A [Member]
Ceded Credit Risk [Line Items]
Reinsurance ceded receivables	$ 242,364	$ 199,479
Reinsurance Recoverables, Percentage of Total	34.90%	31.30%
AM Best, A+ Rating [Member] | Reinsurer B [Member]
Ceded Credit Risk [Line Items]
Reinsurance ceded receivables	$ 189,424	$ 179,522
Reinsurance Recoverables, Percentage of Total	27.30%	28.10%
AM Best, A+ Rating [Member] | Reinsurer C [Member]
Ceded Credit Risk [Line Items]
Reinsurance ceded receivables	$ 69,819	$ 72,836
Reinsurance Recoverables, Percentage of Total	10.00%	11.40%
AM Best, A++ Rating [Member] | Reinsurer E [Member]
Ceded Credit Risk [Line Items]
Reinsurance ceded receivables	$ 34,387	$ 41,807
Reinsurance Recoverables, Percentage of Total	4.90%	6.60%
AM Best, A Rating [Member] | Reinsurer D [Member]
Ceded Credit Risk [Line Items]
Reinsurance ceded receivables	$ 37,634	$ 37,138
Reinsurance Recoverables, Percentage of Total	5.40%	5.80%