Accumulated Other Comprehensive Income (Balance of and Changes in Each Component of AOCI) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended				9 Months Ended
	Sep. 30, 2014		Sep. 30, 2013		Sep. 30, 2014		Sep. 30, 2013
Accumulated Other Comprehensive Income Loss Net Of Tax [Line Items]
Balance, Beginning of Period					$ 1,005,607		$ 2,108,902
Other comprehensive income (loss) before reclassifications					515,949		(1,012,727)
Amounts reclassified from AOCI					(21,949)		3,826
Net current-period other comprehensive income (loss)	(129,053)		(82,133)		494,000		(1,008,901)
Balance, End of Period	1,499,607		1,100,001		1,499,607		1,100,001
Accumulated Currency Translation Adjustments [Member]
Accumulated Other Comprehensive Income Loss Net Of Tax [Line Items]
Balance, Beginning of Period					207,083		267,475
Other comprehensive income (loss) before reclassifications					(75,147)		(75,798)
Amounts reclassified from AOCI					0		0
Net current-period other comprehensive income (loss)					(75,147)		(75,798)
Balance, End of Period	131,936		191,677		131,936		191,677
Unrealized Appreciation Of Securities [Member]
Accumulated Other Comprehensive Income Loss Net Of Tax [Line Items]
Balance, Beginning of Period					820,245	[1]	1,877,657	[1]
Other comprehensive income (loss) before reclassifications					591,373	[1]	(936,847)	[1]
Amounts reclassified from AOCI					(23,661)	[1]	1,527	[1]
Net current-period other comprehensive income (loss)					567,712	[1]	(935,320)	[1]
Balance, End of Period	1,387,957	[1]	942,337	[1]	1,387,957	[1]	942,337	[1]
Pension And Postretirement Benefits [Member]
Accumulated Other Comprehensive Income Loss Net Of Tax [Line Items]
Balance, Beginning of Period					(21,721)		(36,230)
Other comprehensive income (loss) before reclassifications					(277)		(82)
Amounts reclassified from AOCI					1,712		2,299
Net current-period other comprehensive income (loss)					1,435		2,217
Balance, End of Period	$ (20,286)		$ (34,013)		$ (20,286)		$ (34,013)

[1] Includes cash flow hedges. See Note 5 - “Derivative Instruments” for additional information on cash flow hedges.