Supplemental Information about Changes to Accumulated Other Comprehensive Income - Schedule of Change in Balance by Component (Detail) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2020	Mar. 31, 2019
Increase (Decrease) in AOCI, Net of Tax
Beginning balance	$ 7,294,307	$ 5,415,177
Other comprehensive income (loss) before reclassifications, net of tax	(804,312)	550,848
Reclassifications, net of tax	25,729	(256)
Other comprehensive income (loss)	(778,583)	550,592
Ending balance	6,520,282	6,043,426
Total
Increase (Decrease) in AOCI, Net of Tax
Beginning balance	1,844,830	319,475
Ending balance	1,066,247	870,067
Available for Sale Assets
Increase (Decrease) in AOCI, Net of Tax
Beginning balance	1,982,650	435,698
Other comprehensive income (loss) before reclassifications, net of tax	(782,936)	550,934
Reclassifications, net of tax	22,445	(1,931)
Other comprehensive income (loss)	(760,491)	549,003
Ending balance	1,222,159	984,701
Deferred Acquisition Costs
Increase (Decrease) in AOCI, Net of Tax
Beginning balance	(5,916)	(4,163)
Other comprehensive income (loss) before reclassifications, net of tax	303	(2,528)
Reclassifications, net of tax	0	0
Other comprehensive income (loss)	303	(2,528)
Ending balance	(5,613)	(6,691)
Foreign Exchange
Increase (Decrease) in AOCI, Net of Tax
Beginning balance	12,058	6,495
Other comprehensive income (loss) before reclassifications, net of tax	(21,679)	2,442
Reclassifications, net of tax	0	0
Other comprehensive income (loss)	(21,679)	2,442
Ending balance	(9,621)	8,937
Pension Adjustments
Increase (Decrease) in AOCI, Net of Tax
Beginning balance	(143,962)	(118,555)
Other comprehensive income (loss) before reclassifications, net of tax	0	0
Reclassifications, net of tax	3,284	1,675
Other comprehensive income (loss)	3,284	1,675
Ending balance	$ (140,678)	$ (116,880)

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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Amount after tax, before reclassification adjustments, of other comprehensive income (loss), attributable to parent.

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Amount after tax of other comprehensive income (loss) attributable to parent entity.

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Total of all stockholders' equity (deficit) items, net of receivables from officers, directors, owners, and affiliates of the entity which are attributable to the parent. The amount of the economic entity's stockholders' equity attributable to the parent excludes the amount of stockholders' equity which is allocable to that ownership interest in subsidiary equity which is not attributable to the parent (noncontrolling interest, minority interest). This excludes temporary equity and is sometimes called permanent equity.

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