Summary Of Significant Accounting Policies (Narrative) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	May. 01, 2013
Summary of Significant Accounting Policies [Line Items]
Deferred policy acquisition cost amortization period	1 year
Adjustment of redeemable noncontrolling interests	$ 4,144	$ (8,186)	$ 1,963
Tax benefit greater than 50%	50.00%
Insurance premiums revenue recognition period	1 year
Stock-based compensation expense, net of taxes	$ 16,300	18,700	$ 18,400
Cumulative foreign currency translation loss	$ (72,700)	$ (43,500)
Alterra Capital Holdings [Member]
Summary of Significant Accounting Policies [Line Items]
Percentage of issued and outstanding common stock acquired				100.00%