Accumulated Other Comprehensive Income (Balance of and Changes in Each Component of AOCI) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014		Mar. 31, 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	277,236		(126,717)
Amounts reclassified from AOCI	(3,344)		(5,445)
Net current-period other comprehensive income (loss)	273,892		(132,162)
Balance, End of Period	1,279,499		1,976,740
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	(42,683)		(14,105)
Amounts reclassified from AOCI	0		0
Net current-period other comprehensive income (loss)	(42,683)		(14,105)
Balance, End of Period	164,400		253,370
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
Other comprehensive income (loss) before reclassifications	319,758	[1]	(112,711)	[1]
Amounts reclassified from AOCI	(3,924)	[1]	(6,171)	[1]
Net current-period other comprehensive income (loss)	315,834	[1]	(118,882)	[1]
Balance, End of Period	1,136,079	[1]	1,758,775	[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	161		99
Amounts reclassified from AOCI	580		726
Net current-period other comprehensive income (loss)	741		825
Balance, End of Period	$ (20,980)		$ (35,405)

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