Summary of Net Operating Income (Loss) for Segments and Corporate and Other Activities (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
Segment Reporting Information [Line Items]
Net income available to Genworth Financial, Inc.'s common stockholders		$ 267		$ 418		$ (441)		$ (66)		$ (17)		$ 18		$ 168		$ 174		$ 178	$ 343	$ 119
Add: net income (loss) from continuing operations attributable to noncontrolling interests		(1)		18		23		(6)		19		10		15		20		34	64	70
Add: net income from discontinued operations attributable to noncontrolling interests		0		0		0		0		22		30		35		36		0	123	108
Net income		266	[1],[2],[3],[4]	436	[1],[2],[3],[4]	(418)	[1],[2],[3],[4]	(72)	[1],[2],[3],[4]	24	[5],[6]	58	[5],[6]	218	[5],[6]	230	[5],[6]	212	530	297
Income (loss) from discontinued operations, net of taxes		(30)	[3]	1	[3]	(520)	[3]	0	[3]	(31)	[6]	(80)	[6]	60	[6]	62	[6]	(549)	11	230
Income from continuing operations		296	[1],[2],[4]	435	[1],[2],[4]	102	[1],[2],[4]	(72)	[1],[2],[4]	55	[5]	138	[5]	158	[5]	168	[5]	761	519	67
Less: net income (loss) from continuing operations attributable to noncontrolling interests		(1)		18		23		(6)		19		10		15		20		34	64	70
Income (loss) from continuing operations available to Genworth Financial, Inc.'s common stockholders		$ 297		$ 417		$ 79		$ (66)		$ 36		$ 128		$ 143		$ 148		727	455	(3)
Net investment (gains) losses, net	[7]																	(538)	(50)	(10)
Goodwill impairment, net	[8]																	3	0	0
(Gains) losses on early extinguishment of debt, net																		9	0	0
Expenses related to restructuring																		3	4	2
Fees associated with bond consent solicitation																		0	0	6
Taxes on adjustments																		113	11	0
Adjusted operating income (loss) available to Genworth Financial, Inc.'s common stockholders																		317	420	(5)
Segment, Continuing Operations
Segment Reporting Information [Line Items]
Net income																		212	530	297
Income from continuing operations																		761	519	67
Income (loss) from continuing operations available to Genworth Financial, Inc.'s common stockholders																		727	455	(3)
Segment, Continuing Operations | U.S. Mortgage Insurance
Segment Reporting Information [Line Items]
Net income available to Genworth Financial, Inc.'s common stockholders																		378	569	490
Add: net income (loss) from continuing operations attributable to noncontrolling interests																		0	0	0
Net income																		378	569	490
Income from continuing operations																		378	569	490
Less: net income (loss) from continuing operations attributable to noncontrolling interests																		0	0	0
Income (loss) from continuing operations available to Genworth Financial, Inc.'s common stockholders																		378	569	490
Adjusted operating income (loss) available to Genworth Financial, Inc.'s common stockholders																		381	568	490
Segment, Continuing Operations | Australia Mortgage Insurance
Segment Reporting Information [Line Items]
Net income available to Genworth Financial, Inc.'s common stockholders																		23	59	70
Add: net income (loss) from continuing operations attributable to noncontrolling interests																		34	64	70
Net income																		57	123	140
Income from continuing operations																		57	123	140
Less: net income (loss) from continuing operations attributable to noncontrolling interests																		34	64	70
Income (loss) from continuing operations available to Genworth Financial, Inc.'s common stockholders																		23	59	70
Adjusted operating income (loss) available to Genworth Financial, Inc.'s common stockholders																		1	51	76
Segment, Continuing Operations | Long-term Care Insurance
Segment Reporting Information [Line Items]
Adjusted operating income (loss) available to Genworth Financial, Inc.'s common stockholders																		237	57	(348)
Segment, Continuing Operations | Life Insurance
Segment Reporting Information [Line Items]
Adjusted operating income (loss) available to Genworth Financial, Inc.'s common stockholders																		(247)	(181)	(107)
Segment, Continuing Operations | Fixed Annuities
Segment Reporting Information [Line Items]
Adjusted operating income (loss) available to Genworth Financial, Inc.'s common stockholders																		78	69	79
Segment, Continuing Operations | U.S. Life Insurance
Segment Reporting Information [Line Items]
Net income available to Genworth Financial, Inc.'s common stockholders																		478	13	(348)
Add: net income (loss) from continuing operations attributable to noncontrolling interests																		0	0	0
Net income																		478	13	(348)
Income from continuing operations																		478	13	(348)
Less: net income (loss) from continuing operations attributable to noncontrolling interests																		0	0	0
Income (loss) from continuing operations available to Genworth Financial, Inc.'s common stockholders																		478	13	(348)
Adjusted operating income (loss) available to Genworth Financial, Inc.'s common stockholders																		68	(55)	(376)
Segment, Continuing Operations | Runoff
Segment Reporting Information [Line Items]
Net income available to Genworth Financial, Inc.'s common stockholders																		25	39	13
Add: net income (loss) from continuing operations attributable to noncontrolling interests																		0	0	0
Net income																		25	39	13
Income from continuing operations																		25	39	13
Less: net income (loss) from continuing operations attributable to noncontrolling interests																		0	0	0
Income (loss) from continuing operations available to Genworth Financial, Inc.'s common stockholders																		25	39	13
Adjusted operating income (loss) available to Genworth Financial, Inc.'s common stockholders																		43	56	35
Segment, Continuing Operations | Corporate and Other
Segment Reporting Information [Line Items]
Net income available to Genworth Financial, Inc.'s common stockholders																		(726)	(337)	(106)
Add: net income (loss) from continuing operations attributable to noncontrolling interests																		0	0	0
Net income																		(726)	(214)	2
Income from continuing operations																		(177)	(225)	(228)
Less: net income (loss) from continuing operations attributable to noncontrolling interests																		0	0	0
Income (loss) from continuing operations available to Genworth Financial, Inc.'s common stockholders																		(177)	(225)	(228)
Adjusted operating income (loss) available to Genworth Financial, Inc.'s common stockholders																		$ (176)	$ (200)	$ (230)

[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 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 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.

[5] 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.

[6] 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.

[7] For the years ended December 31, 2020, 2019 and 2018, net investment (gains) losses were adjusted for DAC and other intangible amortization and certain benefit reserves of $(11) million, $(11) million and $(12) million, respectively, and adjusted for net investment gains (losses) attributable to noncontrolling interests of $31 million, $11 million and $(7) million, respectively.

[8] For the year ended December 31, 2020, goodwill impairment was adjusted for the portion attributable to noncontrolling interests of $2 million.