Reclassifications In (Out) of Accumulated Other Comprehensive Income (Loss), Net of Taxes (Detail) - USD ($) $ in Millions		3 Months Ended																12 Months Ended
		Dec. 31, 2020	[1],[2],[3]	Sep. 30, 2020	[1],[2],[3]	Jun. 30, 2020	[1],[2],[3]	Mar. 31, 2020	[1],[2],[3]	Dec. 31, 2019	[4]	Sep. 30, 2019	[4]	Jun. 30, 2019	[4]	Mar. 31, 2019	[4]	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net investment income																		$ (3,260)	$ (3,220)	$ (3,121)
Net investment (gains) losses																		(558)	(50)	9
Income taxes																		270	195	70
(Income) loss from continuing operations		$ (296)		$ (435)		$ (102)		$ 72		$ (55)		$ (138)		$ (158)		$ (168)		(761)	(519)	(67)
Amount reclassified from accumulated other comprehensive income (loss) | Net unrealized investment (gains) losses
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net investment (gains) losses	[5]																	(474)	(79)	(23)
Income taxes																		100	17	5
(Income) loss from continuing operations																		(374)	(62)	(18)
Amount reclassified from accumulated other comprehensive income (loss) | Derivatives qualifying as hedges
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Income taxes																		73	60	58
(Income) loss from continuing operations																		(135)	(110)	(104)
Amount reclassified from accumulated other comprehensive income (loss) | Derivatives qualifying as hedges | Interest rate swaps
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net investment income																		(196)	(164)	(153)
Net investment (gains) losses																		$ (12)	$ (6)	$ (9)

[1] Given our assumption that COVID-19 has temporarily decreased the number of new claims submitted, our long-term care insurance business strengthened IBNR reserves in the fourth quarter of 2020 by $47 million. Additionally, our long-term care insurance business recorded a $91 million increase to claim reserves reflecting our assumption that COVID-19 accelerated mortality experience on the most vulnerable claimants, leaving the remaining claim population less likely to terminate compared to the pre-pandemic average population. Our U.S. mortgage insurance business recorded an unfavorable reserve adjustment of $37 million primarily due to slowing cure emergence patterns impacting the frequency of claim. Our Australia mortgage insurance business strengthened its loss reserves by $88 million, including its IBNR reserves, due to a refinement in methodology to better align with historical delinquency behavior, as well as to reflect delayed impacts from higher expected delinquencies and the pressured economic conditions caused by COVID-19. Our life insurance business completed its annual review of assumptions in the fourth quarter of 2020. This review resulted in lower total benefits and expenses of $82 million from a net favorable unlocking in our term universal and universal life insurance products largely attributable to a model refinement in our term universal life insurance product related to persistency and grace period timing and lower projected cost of insurance assessments on our universal life insurance products. In addition, we recorded a DAC impairment of $63 million in our universal life insurance products due principally to lower future estimated gross profits.

[2] In the fourth quarter of 2020, our long-term care insurance business strengthened its reserves by $109 million after-tax. Our U.S. mortgage insurance and Australia mortgage insurance businesses strengthened their loss reserves by $29 million and $62 million, respectively, after-tax. Our life insurance business recorded a $60 million net favorable unlocking, net of taxes, related to its annual review of assumptions. This favorable unlocking in our life insurance business was partially offset by a DAC impairment of $50 million, net of taxes, as a result of recoverability testing. For all of the aforementioned transactions, see above under superscript (2) for additional details.

[3] In the fourth quarter of 2020, we recorded lower net investment gains as compared to the third quarter of 2020. The higher net investment gains recorded in the third quarter of 2020 related to the sale of available-for-sale fixed maturity securities of $330 million driven primarily from the sale of U.S. government securities due to portfolio rebalancing and asset exposure management as a result of the prolonged low interest rate environment. This decrease to total revenues was partially offset by higher net investment income recorded in the fourth quarter of 2020 largely driven by bond calls and mortgage loan repayments of $40 million and limited partnerships of $38 million.

[4] In the fourth quarter of 2019, our life insurance business recorded a $107 million unfavorable unlocking, net of taxes, related to its annual review of assumptions in our universal and term universal life insurance products, as described above. This unfavorable unlocking in our life insurance business was partially offset by a favorable update of $11 million, net of taxes, in our U.S. mortgage insurance business in connection with a review of its single premium earnings pattern and from a favorable reserve adjustment of $10 million, net of taxes.

[5] Amounts exclude adjustments to DAC, PVFP, sales inducements and benefit reserves.