Liability for Policy and Contract Claims (Detail) - USD ($) $ in Millions	Dec. 31, 2023		Dec. 31, 2022	Dec. 31, 2021	Jan. 01, 2021	Dec. 31, 2020
Liability for Claims and Claims Adjustment Expense [Line Items]
Total liability for policy and contract claims	$ 652		$ 683	$ 819	$ 761	$ 761
Enact segment
Liability for Claims and Claims Adjustment Expense [Line Items]
Total liability for policy and contract claims	518	[1]	519
Life and Annuities segment
Liability for Claims and Claims Adjustment Expense [Line Items]
Total liability for policy and contract claims	126		158
Other mortgage insurance business
Liability for Claims and Claims Adjustment Expense [Line Items]
Total liability for policy and contract claims	$ 8		$ 6

[1] Represents the year in which first monthly mortgage payments have been missed by the borrower.