Investments (Schedule Of Net Investment Income) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Net investment income	$ 49,050	$ 43,412	$ 36,793	$ 47,619	$ 47,270	$ 39,271	$ 37,635	$ 33,388	$ 176,874	$ 157,564	$ 167,141
Fixed maturity investments
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Net investment income									149,449	130,380	157,437
Equity securities
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Net investment income									17,581	19,076	17,080
Other invested assets: hedge funds and private equity
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Net investment income									12,564	8,226	6,772
Other invested assets: other private securities
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Net investment income									13,305	14,711	0
Cash and cash equivalents
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Net investment income									2,134	2,010	2,319
Expenses
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Net investment income									$ (18,159)	$ (16,839)	$ (16,467)