Accumulated Other Comprehensive Income (Balance of and Changes in Each Component of AOCI) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended				6 Months Ended
	Jun. 30, 2014		Jun. 30, 2013		Jun. 30, 2014		Jun. 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					646,731		(921,750)
Amounts reclassified from AOCI					(23,678)		(5,018)
Net current-period other comprehensive income (loss)	349,161		(794,606)		623,053		(926,768)
Balance, End of Period	1,628,660		1,182,134		1,628,660		1,182,134
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					(40)		(102,937)
Amounts reclassified from AOCI					0		0
Net current-period other comprehensive income (loss)					(40)		(102,937)
Balance, End of Period	207,043		164,538		207,043		164,538
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					646,777	[1]	(819,019)	[1]
Amounts reclassified from AOCI					(24,698)	[1]	(6,512)	[1]
Net current-period other comprehensive income (loss)					622,079	[1]	(825,531)	[1]
Balance, End of Period	1,442,324	[1]	1,052,126	[1]	1,442,324	[1]	1,052,126	[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					(6)		206
Amounts reclassified from AOCI					1,020		1,494
Net current-period other comprehensive income (loss)					1,014		1,700
Balance, End of Period	$ (20,707)		$ (34,530)		$ (20,707)		$ (34,530)

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