Condensed Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Net income	$ 140,273	$ 138,429	$ 273,814	$ 262,462
Unrealized gains (losses) on securities:
Total unrealized investment gains (losses)	396,929	692,615	611,995	1,157,208
Less applicable tax (expense) benefit	(138,931)	(242,401)	(214,254)	(404,990)
Unrealized investment gains (losses), net of tax	257,998	450,214	397,741	752,218
Unrealized gains (losses) attributable to deferred acquisition costs	(727)	(2,681)	(1,497)	(5,450)
Less applicable tax (expense) benefit	254	938	524	1,907
Unrealized gains (losses) attributable to deferred acquisition costs, net of tax	(473)	(1,743)	(973)	(3,543)
Foreign exchange translation adjustments, other than securities	3,302	5,382	7,516	7,142
Less applicable tax (expense) benefit	(1,153)	(1,898)	(1,581)	(2,438)
Foreign exchange translation adjustments, other than securities, net of tax	2,149	3,484	5,935	4,704
Pension adjustments:
Amortization of pension costs	3,109	2,551	6,218	5,103
Experience gain (loss)	0	105	371	791
Pension adjustments	3,109	2,656	6,589	5,894
Less applicable tax (expense) benefit	(1,088)	(929)	(2,306)	(2,063)
Pension adjustments, net of tax	2,021	1,727	4,283	3,831
Other comprehensive income (loss)	261,695	453,682	406,986	757,210
Comprehensive income (loss)	401,968	592,111	680,800	1,019,672
Securities [Member]
Unrealized gains (losses) on securities:
Unrealized holding gains (losses) arising during period	394,004	695,984	609,531	1,161,141
Reclassification adjustment for (gains) losses on securities included in net income	681	(3,983)	(354)	(4,296)
Reclassification adjustment for amortization of (discount) and premium	(61)	(1,204)	(498)	(2,568)
Foreign exchange adjustment on securities recorded at fair value	230	593	245	1,048
Unrealized gains (losses) on securities	394,854	691,390	608,924	1,155,325
Other Investments [Member]
Unrealized gains (losses) on securities:
Unrealized gains (losses) on other investments	$ 2,075	$ 1,225	$ 3,071	$ 1,883