Comprehensive Income (Loss) (Components Of Comprehensive Income (Loss) In The Consolidated Statements Of Operations) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2010	Sep. 30, 2010	Jun. 30, 2010	Mar. 31, 2010	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Comprehensive Income (Loss) [Abstract]
Net income (loss)	$ 41,042	$ 63,054	$ 131,312	$ (315,894)	$ 302,533	$ 174,200	$ 156,673	$ (22,652)	$ (80,486)	$ 610,754	$ 806,989
URA(D) of investments - temporary									109,928	65,199	550,356
URA(D) of investments - non-credit OTTI									824	7,831	35,563
URA(D) on securities arising during the period									110,752	73,030	585,919
Less: reclassification adjustment for realized losses (gains) included in net income (loss)									(4,193)	(24,593)	50,789
Total URA(D) on securities arising during the period									106,559	48,437	636,708
Foreign currency translation adjustments									(16,429)	16,429	98,931
Pension adjustments									(45,310)	(2,792)	11,466
Total other comprehensive income (loss), before tax									44,820	62,074	747,105
Tax benefit (expense) on URA(D) of investments - temporary									(21,248)	(5,046)	(91,259)
Tax benefit (expense) on URA(D) of investments - non-credit OTTI									66	(1,002)	(3,830)
Tax benefit (expense) on URA(D) on securities arising during the period									(21,182)	(6,048)	(95,089)
Tax reclassification due to realized losses (gains) included in net income (loss)									(5,236)	17,775	(11,674)
Total tax benefit (expense) from URA(D) arising during the period									(26,418)	11,727	(106,763)
Tax benefit (expense) from foreign currency translation									460	(14,558)	(15,128)
Tax benefit (expense) on pension									15,858	977	(4,013)
Total income tax benefit (expense) related to items of other comprehensive income (loss):									(10,100)	(1,854)	(125,904)
Other comprehensive income (loss), net of tax									34,720	60,220	621,201
COMPREHENSIVE INCOME (LOSS)									$ (45,766)	$ 670,974	$ 1,428,190