Condensed Consolidating Balance Sheet (Detail) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017	Sep. 30, 2017	Dec. 31, 2016
Assets
Fixed maturity securities available-for-sale, at fair value	$ 59,404	$ 62,525
Equity securities, at fair value	783	820
Commercial mortgage loans	6,568	6,341
Restricted commercial mortgage loans related to securitization entities	87	107
Policy loans	1,859	1,786
Other invested assets	1,354	1,813
Investments in subsidiaries	0	0
Total investments	70,055	73,392
Cash, cash equivalents and restricted cash	2,505	2,875	$ 2,836	$ 2,784
Accrued investment income	657	644
Deferred acquisition costs	3,336	2,329
Intangible assets and goodwill	355	301
Reinsurance recoverable	17,351	17,569
Other assets	467	453
Intercompany notes receivable	0	0
Deferred tax assets	650	504
Separate account assets	6,745	7,230
Total assets	102,121	105,297
Liabilities and equity
Future policy benefits	38,018	38,472
Policyholder account balances	22,993	24,195
Liability for policy and contract claims	9,844	9,594	9,384	9,256
Unearned premiums	3,668	3,967
Other liabilities	1,830	1,910
Intercompany notes payable	0	0
Borrowings related to securitization entities	20	40
Non-recourse funding obligations	310	310
Long-term borrowings	4,051	4,224
Deferred tax liability	21	27
Separate account liabilities	6,745	7,230
Total liabilities	87,500	89,969
Equity:
Common stock	1	1
Additional paid-in capital	11,983	11,977
Accumulated other comprehensive income (loss)	2,067	3,027
Retained earnings	1,447	1,113
Treasury stock, at cost	(2,700)	(2,700)
Total Genworth Financial, Inc.'s stockholders' equity	12,798	13,418
Noncontrolling interests	1,823	1,910
Total equity	14,621	15,328	15,087	14,467
Total liabilities and equity	102,121	105,297
Reportable Legal Entities | Parent Guarantor
Assets
Fixed maturity securities available-for-sale, at fair value	0	0
Equity securities, at fair value	0	0
Commercial mortgage loans	0	0
Restricted commercial mortgage loans related to securitization entities	0	0
Policy loans	0	0
Other invested assets	0	0
Investments in subsidiaries	12,925	13,561
Total investments	12,925	13,561
Cash, cash equivalents and restricted cash	0	0	0	0
Accrued investment income	0	0
Deferred acquisition costs	0	0
Intangible assets and goodwill	0	0
Reinsurance recoverable	0	0
Other assets	3	3
Intercompany notes receivable	0	0
Deferred tax assets	4	27
Separate account assets	0	0
Total assets	12,932	13,591
Liabilities and equity
Future policy benefits	0	0
Policyholder account balances	0	0
Liability for policy and contract claims	0	0
Unearned premiums	0	0
Other liabilities	6	41
Intercompany notes payable	128	132
Borrowings related to securitization entities	0	0
Non-recourse funding obligations	0	0
Long-term borrowings	0	0
Deferred tax liability	0	0
Separate account liabilities	0	0
Total liabilities	134	173
Equity:
Common stock	1	1
Additional paid-in capital	11,983	11,977
Accumulated other comprehensive income (loss)	2,067	3,027
Retained earnings	1,447	1,113
Treasury stock, at cost	(2,700)	(2,700)
Total Genworth Financial, Inc.'s stockholders' equity	12,798	13,418
Noncontrolling interests	0	0
Total equity	12,798	13,418
Total liabilities and equity	12,932	13,591
Reportable Legal Entities | Issuer
Assets
Fixed maturity securities available-for-sale, at fair value	0	0
Equity securities, at fair value	0	0
Commercial mortgage loans	0	0
Restricted commercial mortgage loans related to securitization entities	0	0
Policy loans	0	0
Other invested assets	77	75
Investments in subsidiaries	11,890	12,867
Total investments	11,967	12,942
Cash, cash equivalents and restricted cash	534	795	754	998
Accrued investment income	0	0
Deferred acquisition costs	0	0
Intangible assets and goodwill	0	0
Reinsurance recoverable	0	0
Other assets	64	54
Intercompany notes receivable	174	155
Deferred tax assets	1,001	0
Separate account assets	0	0
Total assets	13,740	13,946
Liabilities and equity
Future policy benefits	0	0
Policyholder account balances	0	0
Liability for policy and contract claims	0	0
Unearned premiums	0	0
Other liabilities	233	119
Intercompany notes payable	201	259
Borrowings related to securitization entities	0	0
Non-recourse funding obligations	0	0
Long-term borrowings	3,572	3,724
Deferred tax liability	0	(807)
Separate account liabilities	0	0
Total liabilities	4,006	3,295
Equity:
Common stock	0	0
Additional paid-in capital	9,095	9,096
Accumulated other comprehensive income (loss)	2,153	3,037
Retained earnings	(1,514)	(1,482)
Treasury stock, at cost	0	0
Total Genworth Financial, Inc.'s stockholders' equity	9,734	10,651
Noncontrolling interests	0	0
Total equity	9,734	10,651
Total liabilities and equity	13,740	13,946
Reportable Legal Entities | All Other Subsidiaries
Assets
Fixed maturity securities available-for-sale, at fair value	59,604	62,725
Equity securities, at fair value	783	820
Commercial mortgage loans	6,568	6,341
Restricted commercial mortgage loans related to securitization entities	87	107
Policy loans	1,859	1,786
Other invested assets	1,287	1,742
Investments in subsidiaries	0	0
Total investments	70,188	73,521
Cash, cash equivalents and restricted cash	1,971	2,080	2,082	1,786
Accrued investment income	657	647
Deferred acquisition costs	3,336	2,329
Intangible assets and goodwill	355	301
Reinsurance recoverable	17,351	17,569
Other assets	407	397
Intercompany notes receivable	1	59
Deferred tax assets	(355)	477
Separate account assets	6,745	7,230
Total assets	100,656	104,610
Liabilities and equity
Future policy benefits	38,018	38,472
Policyholder account balances	22,993	24,195
Liability for policy and contract claims	9,844	9,594
Unearned premiums	3,668	3,967
Other liabilities	1,609	1,759
Intercompany notes payable	46	23
Borrowings related to securitization entities	20	40
Non-recourse funding obligations	310	310
Long-term borrowings	479	500
Deferred tax liability	21	834
Separate account liabilities	6,745	7,230
Total liabilities	83,753	86,924
Equity:
Common stock	3	3
Additional paid-in capital	18,423	18,420
Accumulated other comprehensive income (loss)	2,072	3,051
Retained earnings	(5,718)	(5,998)
Treasury stock, at cost	0	0
Total Genworth Financial, Inc.'s stockholders' equity	14,780	15,476
Noncontrolling interests	2,123	2,210
Total equity	16,903	17,686
Total liabilities and equity	100,656	104,610
Eliminations
Assets
Fixed maturity securities available-for-sale, at fair value	(200)	(200)
Equity securities, at fair value	0	0
Commercial mortgage loans	0	0
Restricted commercial mortgage loans related to securitization entities	0	0
Policy loans	0	0
Other invested assets	(10)	(4)
Investments in subsidiaries	(24,815)	(26,428)
Total investments	(25,025)	(26,632)
Cash, cash equivalents and restricted cash	0	0	$ 0	$ 0
Accrued investment income	0	(3)
Deferred acquisition costs	0	0
Intangible assets and goodwill	0	0
Reinsurance recoverable	0	0
Other assets	(7)	(1)
Intercompany notes receivable	(175)	(214)
Deferred tax assets	0	0
Separate account assets	0	0
Total assets	(25,207)	(26,850)
Liabilities and equity
Future policy benefits	0	0
Policyholder account balances	0	0
Liability for policy and contract claims	0	0
Unearned premiums	0	0
Other liabilities	(18)	(9)
Intercompany notes payable	(375)	(414)
Borrowings related to securitization entities	0	0
Non-recourse funding obligations	0	0
Long-term borrowings	0	0
Deferred tax liability	0	0
Separate account liabilities	0	0
Total liabilities	(393)	(423)
Equity:
Common stock	(3)	(3)
Additional paid-in capital	(27,518)	(27,516)
Accumulated other comprehensive income (loss)	(4,225)	(6,088)
Retained earnings	7,232	7,480
Treasury stock, at cost	0	0
Total Genworth Financial, Inc.'s stockholders' equity	(24,514)	(26,127)
Noncontrolling interests	(300)	(300)
Total equity	(24,814)	(26,427)
Total liabilities and equity	$ (25,207)	$ (26,850)