Supplemental Information about Changes to Accumulated Other Comprehensive Income - Schedule of Change in Balance by Component (Detail) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Increase (Decrease) in AOCI, Net of Tax
Beginning balance	$ 6,520,282	$ 6,043,426	$ 7,294,307	$ 5,415,177
Other comprehensive income (loss) before reclassifications, net of tax	1,164,881	568,177	360,569	1,119,025
Reclassifications, net of tax	765	1,006	26,494	750
Other comprehensive income (loss)	1,165,646	569,183	387,063	1,119,775
Ending balance	7,848,369	6,700,398	7,848,369	6,700,398
Total
Increase (Decrease) in AOCI, Net of Tax
Beginning balance	1,066,247	870,067	1,844,830	319,475
Ending balance	2,231,893	1,439,250	2,231,893	1,439,250
Available for Sale Assets
Increase (Decrease) in AOCI, Net of Tax
Beginning balance	1,222,159	984,701	1,982,650	435,698
Other comprehensive income (loss) before reclassifications, net of tax	1,151,193	568,073	368,257	1,119,007
Reclassifications, net of tax	(2,520)	(666)	19,925	(2,597)
Other comprehensive income (loss)	1,148,673	567,407	388,182	1,116,410
Ending balance	2,370,832	1,552,108	2,370,832	1,552,108
Deferred Acquisition Costs
Increase (Decrease) in AOCI, Net of Tax
Beginning balance	(5,613)	(6,691)	(5,916)	(4,163)
Other comprehensive income (loss) before reclassifications, net of tax	301	135	604	(2,393)
Reclassifications, net of tax	0	0	0	0
Other comprehensive income (loss)	301	135	604	(2,393)
Ending balance	(5,312)	(6,556)	(5,312)	(6,556)
Foreign Exchange
Increase (Decrease) in AOCI, Net of Tax
Beginning balance	(9,621)	8,937	12,058	6,495
Other comprehensive income (loss) before reclassifications, net of tax	13,387	(31)	(8,292)	2,411
Reclassifications, net of tax	0	0	0	0
Other comprehensive income (loss)	13,387	(31)	(8,292)	2,411
Ending balance	3,766	8,906	3,766	8,906
Pension Adjustments
Increase (Decrease) in AOCI, Net of Tax
Beginning balance	(140,678)	(116,880)	(143,962)	(118,555)
Other comprehensive income (loss) before reclassifications, net of tax	0	0	0	0
Reclassifications, net of tax	3,285	1,672	6,569	3,347
Other comprehensive income (loss)	3,285	1,672	6,569	3,347
Ending balance	$ (137,393)	$ (115,208)	$ (137,393)	$ (115,208)

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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