Condensed Consolidated Statements of Comprehensive Income (Loss) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Net income	$ 173,048	$ 186,566	$ 338,588	$ 371,911
Unrealized gains (losses) on securities:
Unrealized gains (losses)	1,454,011	718,236	491,370	1,413,175
Less applicable tax (expense) benefit	(305,338)	(150,829)	(103,188)	(296,765)
Unrealized gains (losses) on investments, net of tax	1,148,673	567,407	388,182	1,116,410
Deferred acquisition costs:
Unrealized gains (losses) attributable to deferred acquisition costs	382	170	765	(3,029)
Less applicable tax (expense) benefit	(81)	(35)	(161)	636
Unrealized gains (losses) attributable to deferred acquisition costs, net of tax	301	135	604	(2,393)
Foreign exchange translation:
Foreign exchange translation adjustments, other than securities	16,947	(38)	(10,495)	3,051
Less applicable tax (expense) benefit	(3,560)	7	2,203	(640)
Foreign exchange translation adjustments, other than securities, net of tax	13,387	(31)	(8,292)	2,411
Pension:
Amortization of pension costs	4,158	2,118	8,315	4,238
Less applicable tax (expense) benefit	(873)	(446)	(1,746)	(891)
Pension adjustments, net of tax	3,285	1,672	6,569	3,347
Other comprehensive income (loss)	1,165,646	569,183	387,063	1,119,775
Comprehensive income (loss)	1,338,694	755,749	725,651	1,491,686
Securities
Unrealized gains (losses) on securities:
Unrealized holding gains (losses) arising during period	1,459,508	714,862	481,572	1,408,344
Other reclassification adjustments included in net income	(3,190)	(843)	25,222	(3,287)
Foreign exchange adjustment on securities recorded at fair value	233	626	(2,164)	484
Unrealized gains (losses)	1,456,551	714,645	504,630	1,405,541
Other investments
Unrealized gains (losses) on securities:
Unrealized holding gains (losses) arising during period	$ (2,540)	$ 3,591
Unrealized gains (losses)			$ (13,260)	$ 7,634