Statements of Comprehensive Income (Loss) Statements of Comprehensive Income (Loss) (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		Mar. 31, 2014	Mar. 31, 2013
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Accumulated Other Comprehensive Income (Loss), Beginning of Period					$ 189,391
Other comprehensive income (loss)	(60,272)		7,263		84,273		(248,138)
Accumulated Other Comprehensive Income (Loss), End of Period	273,545				273,545
Net investment gains	72,258		43,869		234,180		96,896
Income before income taxes	278,453		198,233		789,492		517,162
Income before taxes	544,303		504,096		1,593,619		1,479,986
Tax effect	(89,662)		(60,045)		(250,840)		(147,249)
After-tax amounts reclassified	188,791		138,188		538,652		369,913
Unrealized investment gains, pre-tax	(25,029)		(59,814)		163,651		(350,968)
Unrealized investment gains, tax effect	12,117		20,935		(55,419)		122,839
Unrealized investment gains, after-tax amounts	(12,912)		(38,879)		108,232		(228,129)
Currency translation adjustment, pre-tax	(49,380)		44,328		(28,590)		(25,451)
Currency translation adjustment, tax effect	0		0		0		0
Change in unrealized currency translation adjustments	(49,380)		44,328		(28,590)		(25,451)
Net pension asset, pre-tax	3,108		2,790		7,125		8,372
Net pension asset, tax effect	(1,088)		(976)		(2,494)		(2,930)
Net pension asset, after-tax amounts	2,020		1,814		4,631		5,442
Other comprehensive income (loss), pre-tax	(71,301)		(12,696)		142,186		(368,047)
Other comprehensive income (loss), tax effect	11,029		19,959		(57,913)		119,909
Accumulated Net Unrealized Investment Gain (Loss) [Member]
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Accumulated Other Comprehensive Income (Loss), Beginning of Period					256,566		517,658		377,673	328,403
Other comprehensive income (loss) before reclassifications	3,099		(10,331)		143,388		(172,276)
Amounts reclassified from AOCI	(16,011)		(28,548)		(35,156)		(55,853)
Other comprehensive income (loss)	(12,912)		(38,879)		108,232		(228,129)
Unrealized investment gain related to non-controlling interest	(82)		(9)		(119)		(14)
Accumulated Other Comprehensive Income (Loss), End of Period	364,679		289,515		364,679		289,515		377,673	328,403
Currency Translation Adjustments [Member]
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Accumulated Other Comprehensive Income (Loss), Beginning of Period					(60,524)		(36,676)		(39,734)	(106,455)
Other comprehensive income (loss) before reclassifications	(49,380)		44,328		(28,590)		(25,451)
Amounts reclassified from AOCI	0		0		0		0
Other comprehensive income (loss)	(49,380)		44,328		(28,590)		(25,451)
Unrealized investment gain related to non-controlling interest	0		0		0		0
Accumulated Other Comprehensive Income (Loss), End of Period	(89,114)		(62,127)		(89,114)		(62,127)		(39,734)	(106,455)
Change in unrealized currency translation adjustments					(28,590)		(25,451)
Net Pension Asset [Member]
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Accumulated Other Comprehensive Income (Loss), Beginning of Period					(6,651)		(15,351)		(4,040)	(11,723)
Other comprehensive income (loss) before reclassifications	0		0		0		0
Amounts reclassified from AOCI	2,020		1,814		4,631		5,442
Other comprehensive income (loss)	2,020		1,814		4,631		5,442
Unrealized investment gain related to non-controlling interest	0		0		0		0
Accumulated Other Comprehensive Income (Loss), End of Period	(2,020)		(9,909)		(2,020)		(9,909)		(4,040)	(11,723)
Accumulated Other Comprehensive Income (Loss) [Member]
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Accumulated Other Comprehensive Income (Loss), Beginning of Period					189,391		465,631		333,899	210,225
Other comprehensive income (loss) before reclassifications	(46,281)		33,997		114,798		(197,727)
Amounts reclassified from AOCI	(13,991)		(26,734)		(30,525)		(50,411)
Other comprehensive income (loss)	(60,272)		7,263		84,273		(248,138)
Unrealized investment gain related to non-controlling interest	(82)		(9)		(119)
Accumulated Other Comprehensive Income (Loss), End of Period	273,545		217,479		273,545		217,479		333,899	210,225
Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Net Unrealized Investment Gain (Loss) [Member]
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Net investment gains	(24,632)	[1]	(43,920)		(54,086)	[1]	(85,928)	[1]
Tax effect	8,621	[2]	15,372	[2]	18,930	[2]	30,075	[2]
After-tax amounts reclassified	(16,011)		(28,548)		(35,156)		(55,853)
Reclassification out of Accumulated Other Comprehensive Income [Member] | Currency Translation Adjustments [Member]
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Income before income taxes	0		0		0		0
Tax effect	0	[2]	0	[2]	0	[2]	0	[2]
After-tax amounts reclassified	0		0		0		0
Reclassification out of Accumulated Other Comprehensive Income [Member] | Net Pension Asset [Member]
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Income before taxes	3,108	[3]	2,790		7,125	[3]	8,372	[3]
Tax effect	(1,088)	[2]	(976)	[2]	(2,494)	[2]	(2,930)	[2]
After-tax amounts reclassified	2,020		1,814		4,631		5,442
Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Other Comprehensive Income (Loss) [Member]
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Income before income taxes	(21,524)		(41,130)		(46,961)		(77,556)
Tax effect	7,533	[2]	14,396	[2]	16,436	[2]	27,145	[2]
After-tax amounts reclassified	$ (13,991)		$ (26,734)		$ (30,525)		$ (50,411)

[1] Net investment gains in the consolidated statements of

[2] Income tax expense in the consolidated statements of income.

[3] Other operating costs and expenses in the consolidated statements of income.