Segment Reporting (Schedule Of Gross Written Premiums Derived From Largest Non-U.S. Market) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Segment Reporting Information [Line Items]
Gross written premium	$ 1,569,791	$ 1,227,645	$ 1,268,698
Percentage threshold of company revenue not exceeded by any other country	20.70%	22.70%	20.60%
United Kingdom Gross Written Premium [Member]
Segment Reporting Information [Line Items]
Gross written premium	$ 740,763	$ 676,490	$ 555,332