Reinsurance Catastrophe Losses (Details) (Catastrophe [Member], USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014 catastrophic_event	Dec. 31, 2013 catastrophic_event	Dec. 31, 2012 catastrophic_event
Liability for Catastrophe Claims [Line Items]
Number of Catastrophic Events	3	3,000	3,000
Catastrophic Event, Incurred Losses and Loss Adjustment Expense	$ 829	$ 3,602	$ 3,666
Catastrophic Events, Impact on Combined Ratio	0.30%	1.80%	3.00%
Catastrophe Loss Size, Range 1 [Member]
Liability for Catastrophe Claims [Line Items]
Number of Catastrophic Events		1,000	2,000
Catastrophic Event, Incurred Losses and Loss Adjustment Expense		1,839	2,896
Catastrophic Events, Impact on Combined Ratio		0.90%	2.40%
Catastrophe Loss Size, Range 2 [Member]
Liability for Catastrophe Claims [Line Items]
Number of Catastrophic Events	3	2,000	1,000
Catastrophic Event, Incurred Losses and Loss Adjustment Expense	$ 829	$ 1,763	$ 770
Catastrophic Events, Impact on Combined Ratio	0.30%	0.90%	0.60%