Formation of Genworth and Basis of Presentation - Additional Information (Detail) $ / shares in Units, $ in Billions		3 Months Ended
	Oct. 21, 2016 USD ($) $ / shares	Mar. 31, 2020 Segment	Dec. 12, 2019 USD ($)	Apr. 01, 2013
Number of operating segments | Segment		4
Genworth Canada MI
Net cash proceeds for sale of mortgage business			$ 1.7
Genworth Holdings
Percentage of subsidiary equity ownership				100.00%
China Oceanwide Holdings Group Co., Ltd. | Definitive Acquisition Agreement
Total transaction value to acquire all of our outstanding common stock	$ 2.7
Per share amount to acquire all of our outstanding common stock | $ / shares	$ 5.43