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, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Increase (Decrease) in AOCI, Net of Tax
Beginning balance	$ 6,894,020	$ 7,832,337	$ 8,642,806	$ 8,771,092
Other comprehensive income (loss) before reclassifications, net of tax	(1,621,291)	721,148	(3,428,910)	(274,147)
Reclassifications, net of tax	20,303	4,616	19,834	(4,818)
Other comprehensive income (loss)	(1,600,988)	725,764	(3,409,076)	(278,965)
Ending balance	5,323,110	8,616,922	5,323,110	8,616,922
Total
Increase (Decrease) in AOCI, Net of Tax
Beginning balance	869,495	2,024,515	2,677,583	3,029,244
Ending balance	(731,493)	2,750,279	(731,493)	2,750,279
Available for Sale Assets
Increase (Decrease) in AOCI, Net of Tax
Beginning balance	950,921	2,166,932	2,765,290	3,175,572
Other comprehensive income (loss) before reclassifications, net of tax	(1,611,891)	715,949	(3,423,076)	(279,148)
Reclassifications, net of tax	17,585	510	14,401	(13,033)
Other comprehensive income (loss)	(1,594,306)	716,459	(3,408,675)	(292,181)
Ending balance	(643,385)	2,883,391	(643,385)	2,883,391
Deferred Acquisition Costs
Increase (Decrease) in AOCI, Net of Tax
Beginning balance	(3,121)	(4,420)	(3,418)	(4,704)
Other comprehensive income (loss) before reclassifications, net of tax	4,803	322	5,100	606
Reclassifications, net of tax	0	0	0	0
Other comprehensive income (loss)	4,803	322	5,100	606
Ending balance	1,682	(4,098)	1,682	(4,098)
Foreign Exchange
Increase (Decrease) in AOCI, Net of Tax
Beginning balance	22,656	22,820	19,387	23,302
Other comprehensive income (loss) before reclassifications, net of tax	(14,203)	4,877	(10,934)	4,395
Reclassifications, net of tax	0	0	0	0
Other comprehensive income (loss)	(14,203)	4,877	(10,934)	4,395
Ending balance	8,453	27,697	8,453	27,697
Pension Adjustments
Increase (Decrease) in AOCI, Net of Tax
Beginning balance	(100,961)	(160,817)	(103,676)	(164,926)
Other comprehensive income (loss) before reclassifications, net of tax	0	0	0	0
Reclassifications, net of tax	2,718	4,106	5,433	8,215
Other comprehensive income (loss)	2,718	4,106	5,433	8,215
Ending balance	$ (98,243)	$ (156,711)	$ (98,243)	$ (156,711)