Summary of Operating Results Related to Discontinued Operations (Detail) - USD ($) $ in Millions		3 Months Ended																12 Months Ended
		Dec. 31, 2020		Sep. 30, 2020		Jun. 30, 2020		Mar. 31, 2020		Dec. 31, 2019		Sep. 30, 2019		Jun. 30, 2019		Mar. 31, 2019		Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Revenues:
Premiums																		$ 4,110	$ 4,037	$ 3,994
Net investment income																		3,260	3,220	3,121
Net investment gains (losses)																		558	50	(9)
Benefits and expenses:
Benefits and other changes in policy reserves																		5,391	5,163	5,606
Acquisition and operating expenses, net of deferrals																		988	962	943
Amortization of deferred acquisition costs and intangibles																		492	441	348
Total benefits and expenses		$ 1,883	[1]	$ 1,835	[1]	$ 1,990	[1]	$ 1,919	[1]	$ 1,957	[2]	$ 1,848	[2]	$ 1,770	[2]	$ 1,807	[2]	7,627	7,382	7,764
Income from discontinued operations, net of taxes		(30)	[3]	1	[3]	(520)	[3]	0	[3]	(31)	[4]	(80)	[4]	60	[4]	62	[4]	(549)	11	230
Less: net income from discontinued operations attributable to noncontrolling interests		0		0		0		0		22		30		35		36		0	123	108
Income (loss) from discontinued operations available to Genworth Financial, Inc.'s common stockholders		$ (30)		$ 1		$ (520)		$ 0		$ (53)		$ (110)		$ 25		$ 26		$ (549)	(112)	122
Assets Held For Sale Related To Discontinued Operations | Canada Mortgage Insurance
Revenues:
Premiums																			466	525
Net investment income																			132	141
Net investment gains (losses)																			(13)	(137)
Total revenues																			585	529
Benefits and expenses:
Benefits and other changes in policy reserves																			79	78
Acquisition and operating expenses, net of deferrals																			64	54
Amortization of deferred acquisition costs and intangibles																			39	43
Interest expense	[5]																		50	43
Total benefits and expenses																			232	218
Income before income taxes and loss on sale	[6]																		353	311
Provision for income taxes																			111	81
Income before loss on sale																			242	230
Loss on sale, net of taxes																			(121)	0
Income from discontinued operations, net of taxes																			121	230
Less: net income from discontinued operations attributable to noncontrolling interests																			123	108
Income (loss) from discontinued operations available to Genworth Financial, Inc.'s common stockholders																			$ (2)	$ 122

[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] Our life insurance business completed its annual review of assumptions in the fourth quarter of 2019, which resulted in higher total benefits and expenses of $145 million from an unfavorable unlocking in our universal and term universal life insurance products driven mostly by the lower interest rate environment.

[3] In the fourth quarter of 2020, we recorded a loss from discontinued operations, net of taxes, of $30 million principally attributed to foreign currency remeasurement losses of $26 million, unfavorable tax charges of $17 million and other expenses of $8 million, mostly consisting of interest expense attributable to the promissory note owed to AXA. These losses were partially offset by derivative hedge gains of $21 million associated with foreign currency forward contracts entered into to mitigate our exposure to the installment payments to be made in British Pounds in 2022. See note 23 for additional details on discontinued operations.

[4] In the fourth quarter of 2019, we recorded an after-tax loss of approximately $110 million principally in connection with pending litigation involving our former lifestyle protection insurance business. See note 20 for additional information related to asserted claims regarding the sale of our lifestyle protection insurance business. We completed the sale of Genworth MI Canada Inc. (“Genworth Canada”) on December 12, 2019 and recorded an incremental gain of $43 million in the fourth quarter of 2019 predominantly related to a favorable tax position refinement. In addition, during the fourth quarter of 2019 through the sale closing date of December 12, 2019, we recorded $36 million of income from discontinued operations attributed to Genworth Canada.

[5] Interest on debt assumed by Brookfield and interest on debt that was repaid as a result of the sale of Genworth Canada was allocated and reported in discontinued operations. The Term Loan, owed by Genworth Holdings and secured by GFIH’s ownership interest in Genworth Canada’s outstanding common shares, was repaid in connection with the close of the Genworth Canada sale. Accordingly, interest expense related to the Term Loan of $34 million and $25 million for the years ended December 31, 2019 and 2018, respectively, was allocated and reported in discontinued operations.

[6] The years ended December 31, 2019 and 2018 include pre-tax income from discontinued operations available to Genworth Financial, Inc.’s common stockholders of $186 million and $167 million, respectively.