Credit Facilities (Summary Of Outstanding Letters Of Credit And Borrowings Of Bermuda Re Letter Of Credit Facility) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Line of Credit Facility [Line Items]
Commitment	$ 1,100,000
Citibank Bilateral Letter Of Credit Agreement One [Member]
Line of Credit Facility [Line Items]
Commitment	300,000	300,000
In Use	112	119
Date of Expiry	Aug. 30, 2015	Aug. 30, 2014
Citibank Bilateral Letter Of Credit Agreement Two [Member]
Line of Credit Facility [Line Items]
In Use	3,672	3,672
Date of Expiry	Nov. 24, 2015	Nov. 24, 2014
Citibank Bilateral Letter Of Credit Agreement Three [Member]
Line of Credit Facility [Line Items]
In Use	70,922	79,336
Date of Expiry	Dec. 31, 2015	Dec. 31, 2014
Citibank Bilateral Letter Of Credit Agreement Four [Member]
Line of Credit Facility [Line Items]
In Use	2,014	1,045
Date of Expiry	Dec. 31, 2016	Dec. 31, 2015
Citibank Bilateral Letter Of Credit Agreement Five [Member]
Line of Credit Facility [Line Items]
In Use	149,353	22,800
Date of Expiry	Dec. 30, 2018	Dec. 31, 2017
Citibank Bilateral Letter Of Credit Agreement Six [Member]
Line of Credit Facility [Line Items]
In Use		129,147
Date of Expiry		Mar. 30, 2018
Citibank Bilateral Agreement [Member]
Line of Credit Facility [Line Items]
Commitment	300,000	300,000
In Use	$ 226,073	$ 236,119