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, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Increase (Decrease) in AOCI, Net of Tax
Beginning balance	$ 5,323,110	$ 8,616,922	$ 8,642,806	$ 8,771,092
Other comprehensive income (loss) before reclassifications, net of tax	(1,092,365)	(81,235)	(4,521,275)	(355,382)
Reclassifications, net of tax	12,309	(7,425)	32,143	(12,243)
Other comprehensive income (loss)	(1,080,056)	(88,660)	(4,489,132)	(367,625)
Ending balance	4,361,598	8,608,151	4,361,598	8,608,151
Total
Increase (Decrease) in AOCI, Net of Tax
Beginning balance	(731,493)	2,750,279	2,677,583	3,029,244
Ending balance	(1,811,549)	2,661,619	(1,811,549)	2,661,619
Available for Sale Assets
Increase (Decrease) in AOCI, Net of Tax
Beginning balance	(643,385)	2,883,391	2,765,290	3,175,572
Other comprehensive income (loss) before reclassifications, net of tax	(1,079,185)	(76,174)	(4,502,261)	(355,322)
Reclassifications, net of tax	9,592	(11,533)	23,993	(24,566)
Other comprehensive income (loss)	(1,069,593)	(87,707)	(4,478,268)	(379,888)
Ending balance	(1,712,978)	2,795,684	(1,712,978)	2,795,684
Deferred Acquisition Costs
Increase (Decrease) in AOCI, Net of Tax
Beginning balance	1,682	(4,098)	(3,418)	(4,704)
Other comprehensive income (loss) before reclassifications, net of tax	3,711	341	8,811	947
Reclassifications, net of tax	0	0	0	0
Other comprehensive income (loss)	3,711	341	8,811	947
Ending balance	5,393	(3,757)	5,393	(3,757)
Foreign Exchange
Increase (Decrease) in AOCI, Net of Tax
Beginning balance	8,453	27,697	19,387	23,302
Other comprehensive income (loss) before reclassifications, net of tax	(16,891)	(5,402)	(27,825)	(1,007)
Reclassifications, net of tax	0	0	0	0
Other comprehensive income (loss)	(16,891)	(5,402)	(27,825)	(1,007)
Ending balance	(8,438)	22,295	(8,438)	22,295
Pension Adjustments
Increase (Decrease) in AOCI, Net of Tax
Beginning balance	(98,243)	(156,711)	(103,676)	(164,926)
Other comprehensive income (loss) before reclassifications, net of tax	0	0	0	0
Reclassifications, net of tax	2,717	4,108	8,150	12,323
Other comprehensive income (loss)	2,717	4,108	8,150	12,323
Ending balance	$ (95,526)	$ (152,603)	$ (95,526)	$ (152,603)