Other Comprehensive Income (Details) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Components of Other Comprehensive Income (Loss) [Abstract]
Net unrealized holding (losses) gains arising during the period		$ (64,118)	$ 44,818	$ (44,397)	$ 84,479
Income tax benefit (expense)		22,362	(15,634)	15,486	(29,505)
Valuation allowance		(21,890)	15,317	(15,172)	29,125
Net of taxes		(63,646)	44,501	(44,083)	84,099
Net changes in benefit plan assets and obligations		(392)	(1,980)	(1,092)	(3,466)
Income tax benefit		137	693	382	1,213
Valuation allowance		(137)	(693)	(382)	(1,213)
Net of taxes		(392)	(1,980)	(1,092)	(3,466)
Net changes in unrealized foreign currency translation adjustment		598	904	(2,504)	2,835
Income tax benefit (expense)		(208)	(317)	880	(995)
Net of taxes		390	587	(1,624)	1,840
Total other comprehensive income (loss)		(63,912)	43,742	(47,993)	83,848
Total income tax benefit (expense), net of valuation allowance		264	(634)	1,194	(1,375)
Other comprehensive (loss) income, net of tax		(63,648)	43,108	(46,799)	82,473
Amounts Reclassified From Accumulated Other Comprehensive Income [Abstract]
Total reclassifications		114,976	46,640	251,437	107,348
Income tax (expense) benefit		(39,991)	(17,172)	(87,874)	(40,292)
Valuation allowance		(38,669)	(16,054)	(83,167)	(38,448)
Total income tax expense, net of valuation allowance		1,322	1,118	4,707	1,844
Net of taxes		113,654	45,522	246,730	105,504
Accumulated Other Comprehensive Loss, Net of Tax [Roll Forward]
Balance at beginning of period, net of tax				(81,341)
Other comprehensive loss before reclassifications				(34,040)
Less: Amounts reclassified from AOCL				12,759
Balance at end of period, net of tax		(128,140)		(128,140)
Reclassification from Accumulated Other Comprehensive Income [Member]
Amounts Reclassified From Accumulated Other Comprehensive Income [Abstract]
Total reclassifications		869	84	12,803	(1,419)
Total income tax expense, net of valuation allowance		(39)	(30)	(44)	(30)
Net of taxes		830	54	12,759	(1,449)
Unrealized Gains and Losses on Available-for-Sale Securities [Member]
Accumulated Other Comprehensive Loss, Net of Tax [Roll Forward]
Balance at beginning of period, net of tax				(57,551)
Other comprehensive loss before reclassifications				(32,416)
Less: Amounts reclassified from AOCL	[1]			11,667
Balance at end of period, net of tax		(101,634)		(101,634)
Unrealized Gains and Losses on Available-for-Sale Securities [Member] | Reclassification from Accumulated Other Comprehensive Income [Member]
Amounts Reclassified From Accumulated Other Comprehensive Income [Abstract]
Total reclassifications		477	(1,896)	11,711	(4,885)
Income tax (expense) benefit		(161)	669	(4,092)	1,715
Valuation allowance		122	(699)	4,048	(1,745)
Net of taxes		438	(1,926)	11,667	(4,915)
Defined Benefit Plans [Member]
Accumulated Other Comprehensive Loss, Net of Tax [Roll Forward]
Balance at beginning of period, net of tax				(28,938)
Other comprehensive loss before reclassifications				0
Less: Amounts reclassified from AOCL	[2]			1,092
Balance at end of period, net of tax		(30,030)		(30,030)
Defined Benefit Plans [Member] | Reclassification from Accumulated Other Comprehensive Income [Member]
Amounts Reclassified From Accumulated Other Comprehensive Income [Abstract]
Total reclassifications		392	1,980	1,092	3,466
Income tax (expense) benefit		(137)	(693)	(382)	(1,213)
Valuation allowance		137	693	382	1,213
Net of taxes		392	$ 1,980	1,092	$ 3,466
Foreign Currency Translation [Member]
Accumulated Other Comprehensive Loss, Net of Tax [Roll Forward]
Balance at beginning of period, net of tax				5,148
Other comprehensive loss before reclassifications				(1,624)
Less: Amounts reclassified from AOCL				0
Balance at end of period, net of tax		$ 3,524		$ 3,524

[1] Increases Net realized investment gains on the Consolidated Statements of Operations.

[2] Decreases Other underwriting and operating expenses, net on the Consolidated Statements of Operations.