Segment Reporting (Schedule Of Underwriting Results For Operating Segments To Income (Loss) Before Taxes) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Segment Reporting [Abstract]
Underwriting gain (loss)									$ 246,784	$ 42,851	$ (576,734)
Net investment income	69,563	68,828	81,736	76,869	74,355	76,342	74,206	81,242	296,996	306,145	312,933
Net realized capital gains (losses)	189,391	208,426	15,526	309,806	37,029	95,943	82,589	176,141	723,149	391,702	(41,116)
Corporate expense									(8,262)	(8,764)	(6,073)
Interest, fee and bond issue cost amortization expense									(45,452)	(50,746)	(50,763)
Other income (expense)									(7,714)	12,136	(11,745)
Income (loss) before taxes									$ 1,205,501	$ 693,324	$ (373,498)