Condensed Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Net income	$ 173,600	$ 133,541
Investments:
Total unrealized investment gains (losses)	(615,682)	215,066
Less applicable tax (expense) benefit	129,289	(75,323)
Unrealized investment gains (losses), net of tax	(486,393)	139,743
Deferred acquisition costs:
Unrealized gains (losses) attributable to deferred acquisition costs	450	(770)
Less applicable tax (expense) benefit	(94)	270
Unrealized gains (losses) attributable to deferred acquisition costs, net of tax	356	(500)
Foreign exchange translation:
Foreign exchange translation adjustments, other than securities	(1,299)	4,214
Less applicable tax (expense) benefit	276	(428)
Foreign exchange translation adjustments, other than securities, net of tax	(1,023)	3,786
Pension:
Amortization of pension costs	3,778	3,109
Experience gain (loss)	0	371
Pension adjustments	3,778	3,480
Less applicable tax (expense) benefit	(793)	(1,218)
Pension adjustments, net of tax	2,985	2,262
Other comprehensive income (loss)	(484,075)	145,291
Comprehensive income (loss)	(310,475)	278,832
Securities [Member]
Investments:
Unrealized holding gains (losses) arising during period	(611,548)	215,527
Reclassification adjustment for (gains) losses on securities included in net income	(1,386)	(1,035)
Reclassification adjustment for amortization of (discount) and premium	690	(437)
Foreign exchange adjustment on securities recorded at fair value	(585)	15
Unrealized gains (losses) on securities	(612,829)	214,070
Other Investments [Member]
Investments:
Unrealized gains (losses) on other investments	$ (2,853)	$ 996