Accumulated Other Comprehensive Income (Components of Accumulated Other Comprehensive Income, Net of Tax) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance at December 31, 2015	$ 4,523,967
Total other comprehensive income (loss)	106,691	$ (6,770)
Balance, March 31, 2016	4,564,645
Foreign currency translation adjustment
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance at December 31, 2015	(270,734)	(127,711)
Other comprehensive loss before reclassifications	11,860	(65,951)
Amounts reclassified from accumulated other comprehensive income	0	0
Total other comprehensive income (loss)	11,860	(65,951)
Balance, March 31, 2016	(258,874)	(193,662)
Unrealized gains on securities
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance at December 31, 2015	495,443	793,082
Other comprehensive loss before reclassifications	(66,262)	53,523
Amounts reclassified from accumulated other comprehensive income	96,134	3,936
Total other comprehensive income (loss)	29,872	57,459
Balance, March 31, 2016	525,315	850,541
OTTI
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance at December 31, 2015	22,434	26,594
Other comprehensive loss before reclassifications	(970)	777
Amounts reclassified from accumulated other comprehensive income	(281)	(1,671)
Total other comprehensive income (loss)	(1,251)	(894)
Balance, March 31, 2016	21,183	25,700
Pension under- funding
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance at December 31, 2015	(128,594)	(136,198)
Other comprehensive loss before reclassifications	85,029	0
Amounts reclassified from accumulated other comprehensive income	(18,819)	2,616
Total other comprehensive income (loss)	66,210	2,616
Balance, March 31, 2016	(62,384)	(133,582)
Accumulated Other Comprehensive Income
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance at December 31, 2015	118,549	555,767
Other comprehensive loss before reclassifications	29,657	(11,651)
Amounts reclassified from accumulated other comprehensive income	77,034	4,881
Total other comprehensive income (loss)	106,691	(6,770)
Balance, March 31, 2016	$ 225,240	$ 548,997