Investments (Schedule Of Trading Securities) (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Equity securities and other invested assets [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading securities, Fair Value	$ 1,751,200	$ 1,463,927
Trading securities, Amortized Cost	1,603,094	1,305,984
Equity securities [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading securities, Fair Value	945,076	699,846
Trading securities, Amortized Cost	901,300	647,301
Other invested assets [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading securities, Fair Value	806,124	764,081
Trading securities, Amortized Cost	701,794	658,683
Fixed maturity investments [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading securities, Fair Value	6,128,237	6,100,798
Trading securities, Amortized Cost	6,074,752	6,065,350
U.S. Government And Government Agencies [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading securities, Fair Value	1,184,115	1,676,788
Trading securities, Amortized Cost	1,186,185	1,684,832
Non-U.S. Government And Government Agencies [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading securities, Fair Value	219,287	191,776
Trading securities, Amortized Cost	229,792	197,082
States, Municipalities And Political Subdivisions [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading securities, Fair Value	260,690	231,555
Trading securities, Amortized Cost	251,628	234,406
Corporate Debt, Financial Institutions [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading securities, Fair Value	1,194,949	958,794
Trading securities, Amortized Cost	1,185,637	943,518
Corporate Debt, Industrials [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading securities, Fair Value	1,202,906	1,174,047
Trading securities, Amortized Cost	1,201,341	1,165,448
Corporate Debt, Utilities [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading securities, Fair Value	125,513	69,426
Trading securities, Amortized Cost	125,202	69,658
Mortgage-Backed [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading securities, Fair Value	1,240,362	1,292,502
Trading securities, Amortized Cost	1,196,683	1,267,863
Asset-Backed [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading securities, Fair Value	700,415	505,910
Trading securities, Amortized Cost	$ 698,284	$ 502,543