Reinsurance Reinsurance (Ceded Reinsurance Receivable Assets) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Ceded Credit Risk [Line Items]
Reinsurance ceded receivables	$ 683,972	$ 637,859
Reinsurance Recoverables, Percentage of Total	100.00%	100.00%
Other Reinsurers [Member]
Ceded Credit Risk [Line Items]
Reinsurance ceded receivables	$ 118,679	$ 107,077
Reinsurance Recoverables, Percentage of Total	17.30%	16.80%
AM Best, A+ Rating [Member] | Reinsurer A [Member]
Ceded Credit Risk [Line Items]
Reinsurance ceded receivables	$ 240,894	$ 199,479
Reinsurance Recoverables, Percentage of Total	35.20%	31.30%
AM Best, A+ Rating [Member] | Reinsurer B [Member]
Ceded Credit Risk [Line Items]
Reinsurance ceded receivables	$ 183,881	$ 179,522
Reinsurance Recoverables, Percentage of Total	26.90%	28.10%
AM Best, A+ Rating [Member] | Reinsurer C [Member]
Ceded Credit Risk [Line Items]
Reinsurance ceded receivables	$ 68,832	$ 72,836
Reinsurance Recoverables, Percentage of Total	10.10%	11.40%
AM Best, A++ Rating [Member] | Reinsurer D [Member]
Ceded Credit Risk [Line Items]
Reinsurance ceded receivables	$ 36,202	$ 41,807
Reinsurance Recoverables, Percentage of Total	5.30%	6.60%
AM Best, A Rating [Member] | Reinsurer E [Member]
Ceded Credit Risk [Line Items]
Reinsurance ceded receivables	$ 35,484	$ 37,138
Reinsurance Recoverables, Percentage of Total	5.20%	5.80%