Incurred Claims, Net of Reinsurance, Cumulative Number of Reported Delinquencies and Total of Incurred-But-Not-Reported Liabilities (Detail) - Enact Segment $ in Millions		Dec. 31, 2022 USD ($) Claim	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)
Claims Development [Line Items]
Incurred claims and allocated claim adjustment expenses, net of reinsurance	[1]	$ 1,645
Accident Year 2013
Claims Development [Line Items]
Incurred claims and allocated claim adjustment expenses, net of reinsurance	[1]	381	$ 381	$ 381	$ 381	$ 382	$ 384	$ 387	$ 392	$ 407	$ 475
Total of IBNR liabilities including expected development on reported claims
Number of reported delinquencies | Claim	[2]	22,502
Accident Year 2014
Claims Development [Line Items]
Incurred claims and allocated claim adjustment expenses, net of reinsurance	[1]	$ 258	259	259	258	259	261	269	288	328	0
Total of IBNR liabilities including expected development on reported claims
Number of reported delinquencies | Claim	[2]	17,809
Accident Year 2015
Claims Development [Line Items]
Incurred claims and allocated claim adjustment expenses, net of reinsurance	[1]	$ 179	179	180	180	181	187	208	235	0	0
Total of IBNR liabilities including expected development on reported claims
Number of reported delinquencies | Claim	[2]	15,400
Accident Year 2016
Claims Development [Line Items]
Incurred claims and allocated claim adjustment expenses, net of reinsurance	[1]	$ 135	136	137	136	138	160	198	0	0	0
Total of IBNR liabilities including expected development on reported claims
Number of reported delinquencies | Claim	[2]	13,970
Accident Year 2017
Claims Development [Line Items]
Incurred claims and allocated claim adjustment expenses, net of reinsurance	[1]	$ 102	104	105	102	121	171	0	0	0	0
Total of IBNR liabilities including expected development on reported claims
Number of reported delinquencies | Claim	[2]	15,097
Accident Year 2018
Claims Development [Line Items]
Incurred claims and allocated claim adjustment expenses, net of reinsurance	[1]	$ 73	78	84	84	117	0	0	0	0	0
Total of IBNR liabilities including expected development on reported claims
Number of reported delinquencies | Claim	[2]	11,269
Accident Year 2019
Claims Development [Line Items]
Incurred claims and allocated claim adjustment expenses, net of reinsurance	[1]	$ 71	98	111	106	0	0	0	0	0	0
Total of IBNR liabilities including expected development on reported claims
Number of reported delinquencies | Claim	[2]	11,883
Accident Year 2020
Claims Development [Line Items]
Incurred claims and allocated claim adjustment expenses, net of reinsurance	[1]	$ 107	362	365	0	0	0	0	0	0	0
Total of IBNR liabilities including expected development on reported claims
Number of reported delinquencies | Claim	[2]	38,863
Accident Year 2021
Claims Development [Line Items]
Incurred claims and allocated claim adjustment expenses, net of reinsurance	[1]	$ 119	141	0	0	0	0	0	0	0	0
Total of IBNR liabilities including expected development on reported claims		$ 1
Number of reported delinquencies | Claim	[2]	12,585
Accident Year 2022
Claims Development [Line Items]
Incurred claims and allocated claim adjustment expenses, net of reinsurance	[1]	$ 220	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0
Total of IBNR liabilities including expected development on reported claims		$ 24
Number of reported delinquencies | Claim	[2]	14,329

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

[2] Represents reported and outstanding delinquencies less actual cures as of December 31 for each respective accident year.