Supplemental Information about Changes to Accumulated Other Comprehensive Income - Schedule of Change in Balance by Component (Detail) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Increase (Decrease) in AOCI, Net of Tax
Beginning balance	$ 7,848,369	$ 6,700,398	$ 7,294,307	$ 5,415,177
Other comprehensive income (loss) before reclassifications, net of tax	306,091	510,906	666,660	1,629,931
Reclassifications, net of tax	12,635	(7,032)	39,129	(6,282)
Other comprehensive income (loss)	318,726	503,874	705,789	1,623,649
Ending balance	8,224,908	7,312,531	8,224,908	7,312,531
Total
Increase (Decrease) in AOCI, Net of Tax
Beginning balance	2,231,893	1,439,250	1,844,830	319,475
Ending balance	2,550,619	1,943,124	2,550,619	1,943,124
Available for Sale Assets
Increase (Decrease) in AOCI, Net of Tax
Beginning balance	2,370,832	1,552,108	1,982,650	435,698
Other comprehensive income (loss) before reclassifications, net of tax	301,423	513,812	669,680	1,632,819
Reclassifications, net of tax	9,352	(8,706)	29,277	(11,303)
Other comprehensive income (loss)	310,775	505,106	698,957	1,621,516
Ending balance	2,681,607	2,057,214	2,681,607	2,057,214
Deferred Acquisition Costs
Increase (Decrease) in AOCI, Net of Tax
Beginning balance	(5,312)	(6,556)	(5,916)	(4,163)
Other comprehensive income (loss) before reclassifications, net of tax	304	318	908	(2,075)
Reclassifications, net of tax	0	0	0	0
Other comprehensive income (loss)	304	318	908	(2,075)
Ending balance	(5,008)	(6,238)	(5,008)	(6,238)
Foreign Exchange
Increase (Decrease) in AOCI, Net of Tax
Beginning balance	3,766	8,906	12,058	6,495
Other comprehensive income (loss) before reclassifications, net of tax	4,364	(3,224)	(3,928)	(813)
Reclassifications, net of tax	0	0	0	0
Other comprehensive income (loss)	4,364	(3,224)	(3,928)	(813)
Ending balance	8,130	5,682	8,130	5,682
Pension Adjustments
Increase (Decrease) in AOCI, Net of Tax
Beginning balance	(137,393)	(115,208)	(143,962)	(118,555)
Other comprehensive income (loss) before reclassifications, net of tax	0	0	0	0
Reclassifications, net of tax	3,283	1,674	9,852	5,021
Other comprehensive income (loss)	3,283	1,674	9,852	5,021
Ending balance	$ (134,110)	$ (113,534)	$ (134,110)	$ (113,534)

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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