Condensed Consolidating Income Statement (Detail) - USD ($) $ in Millions	3 Months Ended																12 Months Ended
	Dec. 31, 2017		Sep. 30, 2017		Jun. 30, 2017		Mar. 31, 2017		Dec. 31, 2016		Sep. 30, 2016		Jun. 30, 2016		Mar. 31, 2016		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Revenues:
Premiums																	$ 4,004	$ 4,160	$ 4,579
Net investment income																	3,200	3,159	3,138
Net investment gains (losses)																	265	72	(75)
Policy fees and other income																	826	978	906
Total revenues	$ 1,686	[1]	$ 2,215	[1]	$ 2,223	[1]	$ 2,171	[1]	$ 2,198	[2]	$ 2,150	[2]	$ 2,236	[2]	$ 1,785	[2]	8,295	8,369	8,548
Benefits and expenses:
Benefits and other changes in policy reserves																	5,179	5,245	5,149
Interest credited																	646	696	720
Acquisition and operating expenses, net of deferrals																	1,022	1,273	1,309
Amortization of deferred acquisition costs and intangibles																	435	498	966
Interest expense																	284	337	419
Total benefits and expenses	1,976	[3]	1,929	[3]	1,822	[3]	1,839	[3]	2,254	[4]	2,275	[4]	1,885	[4]	1,635	[4]	7,566	8,049	8,563
Income (loss) from continuing operations before income taxes																	729	320	(15)
Provision (benefit) for income taxes	456																(207)	358	(9)
Equity in income (loss) of subsidiaries																	0	0	0
Income (loss) from continuing operations	265	[5]	184	[5]	271	[5]	216	[5]	(59)	[6]	(347)	[6]	241	[6]	127	[6]	936	(38)	(6)
Income (loss) from discontinued operations, net of taxes	0		(9)		0		0		(4)		15		(21)		(19)		(9)	(29)	(407)
Net income (loss)	265	[5]	175	[5]	271	[5]	216	[5]	(63)	[6]	(332)	[6]	220	[6]	108	[6]	927	(67)	(413)
Less: net income attributable to noncontrolling interests	(88)	[7]	68	[7]	69	[7]	61	[7]	59		48		48		55		110	210	202
Net income (loss) available to Genworth Financial, Inc.'s common stockholders	$ 353	[5]	$ 107	[5]	$ 202	[5]	$ 155	[5]	$ (122)		$ (380)		$ 172		$ 53		817	(277)	(615)
Reportable Legal Entities | Parent Guarantor
Revenues:
Premiums																	0	0	0
Net investment income																	(3)	(3)	(3)
Net investment gains (losses)																	0	0	0
Policy fees and other income																	0	0	0
Total revenues																	(3)	(3)	(3)
Benefits and expenses:
Benefits and other changes in policy reserves																	0	0	0
Interest credited																	0	0	0
Acquisition and operating expenses, net of deferrals																	57	153	32
Amortization of deferred acquisition costs and intangibles																	0	0	0
Interest expense																	1	1	0
Total benefits and expenses																	58	154	32
Income (loss) from continuing operations before income taxes																	(61)	(157)	(35)
Provision (benefit) for income taxes																	0	(47)	(8)
Equity in income (loss) of subsidiaries																	878	(166)	(579)
Income (loss) from continuing operations																	817	(276)	(606)
Income (loss) from discontinued operations, net of taxes																	0	(1)	(9)
Net income (loss)																	817	(277)	(615)
Less: net income attributable to noncontrolling interests																	0	0	0
Net income (loss) available to Genworth Financial, Inc.'s common stockholders																	817	(277)	(615)
Reportable Legal Entities | Issuer
Revenues:
Premiums																	0	0	0
Net investment income																	8	2	1
Net investment gains (losses)																	(14)	(1)	43
Policy fees and other income																	5	(8)	(32)
Total revenues																	(1)	(7)	12
Benefits and expenses:
Benefits and other changes in policy reserves																	0	0	0
Interest credited																	0	0	0
Acquisition and operating expenses, net of deferrals																	(2)	38	2
Amortization of deferred acquisition costs and intangibles																	0	0	0
Interest expense																	254	278	307
Total benefits and expenses																	252	316	309
Income (loss) from continuing operations before income taxes																	(253)	(323)	(297)
Provision (benefit) for income taxes																	(67)	71	(103)
Equity in income (loss) of subsidiaries																	771	(53)	(463)
Income (loss) from continuing operations																	585	(447)	(657)
Income (loss) from discontinued operations, net of taxes																	4	(12)	0
Net income (loss)																	589	(459)	(657)
Less: net income attributable to noncontrolling interests																	0	0	0
Net income (loss) available to Genworth Financial, Inc.'s common stockholders																	589	(459)	(657)
Reportable Legal Entities | All Other Subsidiaries
Revenues:
Premiums																	4,004	4,160	4,579
Net investment income																	3,210	3,175	3,154
Net investment gains (losses)																	279	73	(118)
Policy fees and other income																	823	986	940
Total revenues																	8,316	8,394	8,555
Benefits and expenses:
Benefits and other changes in policy reserves																	5,179	5,245	5,149
Interest credited																	646	696	720
Acquisition and operating expenses, net of deferrals																	967	1,082	1,275
Amortization of deferred acquisition costs and intangibles																	435	498	966
Interest expense																	46	73	128
Total benefits and expenses																	7,273	7,594	8,238
Income (loss) from continuing operations before income taxes																	1,043	800	317
Provision (benefit) for income taxes																	(140)	334	102
Equity in income (loss) of subsidiaries																	0	0	0
Income (loss) from continuing operations																	1,183	466	215
Income (loss) from discontinued operations, net of taxes																	(13)	(16)	(398)
Net income (loss)																	1,170	450	(183)
Less: net income attributable to noncontrolling interests																	110	210	202
Net income (loss) available to Genworth Financial, Inc.'s common stockholders																	1,060	240	(385)
Eliminations
Revenues:
Premiums																	0	0	0
Net investment income																	(15)	(15)	(14)
Net investment gains (losses)																	0	0	0
Policy fees and other income																	(2)	0	(2)
Total revenues																	(17)	(15)	(16)
Benefits and expenses:
Benefits and other changes in policy reserves																	0	0	0
Interest credited																	0	0	0
Acquisition and operating expenses, net of deferrals																	0	0	0
Amortization of deferred acquisition costs and intangibles																	0	0	0
Interest expense																	(17)	(15)	(16)
Total benefits and expenses																	(17)	(15)	(16)
Income (loss) from continuing operations before income taxes																	0	0	0
Provision (benefit) for income taxes																	0	0	0
Equity in income (loss) of subsidiaries																	(1,649)	219	1,042
Income (loss) from continuing operations																	(1,649)	219	1,042
Income (loss) from discontinued operations, net of taxes																	0	0	0
Net income (loss)																	(1,649)	219	1,042
Less: net income attributable to noncontrolling interests																	0	0	0
Net income (loss) available to Genworth Financial, Inc.'s common stockholders																	$ (1,649)	$ 219	$ 1,042

[1] Our Australian mortgage insurance business completed a review of its premium earnings pattern in the fourth quarter of 2017 and recorded $468 million of lower earned premiums. The review indicated an observed and expected continuation of a longer duration between policy inception and first loss event.

[2] Our life insurance business completed its annual review of assumptions in the fourth quarter of 2016, which resulted in higher revenues of $6 million in our universal life insurance products. The updated assumptions reflected changes primarily to mortality experience in older age populations and modest updates related to long-term interest rates, lapses and other refinements.

[3] Our life insurance business completed its annual review of assumptions in the fourth quarter of 2017, which resulted in higher total benefits and expenses of $117 million in our universal and term universal life insurance products driven mostly by emerging mortality experience and from prolonged low interest rates. In addition, we recorded lower total benefits and expenses of $18 million in our Australian mortgage insurance business associated with changes to their premium earnings pattern, as described above.

[4] Our life insurance business completed its annual review of assumptions in the fourth quarter of 2016 as described above, which resulted in higher total benefits and expenses of $307 million in our universal and term universal life insurance products.

[5] In the fourth quarter of 2017, we recorded $456 million of net tax benefits primarily from changes in U.S. tax legislation under the TCJA and other items. These tax benefits were mostly related to a $258 million release of a valuation allowance recorded in 2016, the impact from changes in the federal tax rate and the release of shareholder liability taxes, partially offset by higher transition taxes. Our valuation allowance was reduced by $258 million principally related to the TCJA and from improvements in business performance, mostly in our U.S. mortgage insurance business, as well as lower operating earnings volatility in our U.S. life insurance businesses. Our Australian mortgage insurance business completed a review of the premium earnings pattern, as described above, which resulted in an unfavorable adjustment of $152 million, net of taxes and noncontrolling interests. A portion of this loss, $11 million, was recorded in Corporate and Other activities in connection with our allocation methodology for income taxes. We also completed our annual review of assumptions in our life insurance business in the fourth quarter of 2017, as described above, which resulted in a $74 million unfavorable adjustment, net of taxes, in our universal and term universal life insurance products.

[6] Our life insurance business completed its annual review of assumptions in the fourth quarter of 2016 as described above, which resulted in $196 million, net of taxes, of charges in our universal and term universal life insurance products.

[7] We completed a review of the premium earnings pattern in our Australian mortgage insurance business, as described above, which resulted in an unfavorable adjustment to net income (loss) attributable to noncontrolling interests of $151 million.