Reinsurance - Essent Guaranty's Excess of Loss Reinsurance Coverages and Retentions (Details) $ in Thousands	6 Months Ended
	Jun. 30, 2021 USD ($)
SEC Schedule, 12-17, Insurance Companies, Reinsurance [Line Items]
Remaining Insurance in Force	$ 147,212,821
Remaining Risk in Force	36,896,741
Remaining Reinsurance in Force	2,448,125
Remaining First Layer Retention	1,635,129
ILN
SEC Schedule, 12-17, Insurance Companies, Reinsurance [Line Items]
Remaining Reinsurance in Force	2,151,712
Other Reinsurance
SEC Schedule, 12-17, Insurance Companies, Reinsurance [Line Items]
Remaining Reinsurance in Force	296,413
2015 & 2016
SEC Schedule, 12-17, Insurance Companies, Reinsurance [Line Items]
Remaining Insurance in Force	12,018,660
Remaining Risk in Force	3,243,956
Remaining Reinsurance in Force	216,480
Remaining First Layer Retention	207,359
2015 & 2016 | ILN 2015 & 2016
SEC Schedule, 12-17, Insurance Companies, Reinsurance [Line Items]
Remaining Reinsurance in Force	216,480
2015 & 2016 | Other Reinsurance
SEC Schedule, 12-17, Insurance Companies, Reinsurance [Line Items]
Remaining Reinsurance in Force	0
2017
SEC Schedule, 12-17, Insurance Companies, Reinsurance [Line Items]
Remaining Insurance in Force	11,155,879
Remaining Risk in Force	2,865,141
Remaining Reinsurance in Force	407,290
Remaining First Layer Retention	217,930
2017 | Radnor Re 2018-1 Ltd.
SEC Schedule, 12-17, Insurance Companies, Reinsurance [Line Items]
Remaining Reinsurance in Force	242,123
2017 | Other Reinsurance
SEC Schedule, 12-17, Insurance Companies, Reinsurance [Line Items]
Remaining Reinsurance in Force	165,167
2018
SEC Schedule, 12-17, Insurance Companies, Reinsurance [Line Items]
Remaining Insurance in Force	12,752,743
Remaining Risk in Force	3,245,746
Remaining Reinsurance in Force	401,681
Remaining First Layer Retention	249,912
2018 | Radnor Re 2019-1 Ltd.
SEC Schedule, 12-17, Insurance Companies, Reinsurance [Line Items]
Remaining Reinsurance in Force	325,537
2018 | Other Reinsurance
SEC Schedule, 12-17, Insurance Companies, Reinsurance [Line Items]
Remaining Reinsurance in Force	76,144
2019
SEC Schedule, 12-17, Insurance Companies, Reinsurance [Line Items]
Remaining Insurance in Force	15,581,172
Remaining Risk in Force	3,979,796
Remaining Reinsurance in Force	550,991
Remaining First Layer Retention	215,282
2019 | Radnor Re 2020-1 Ltd.
SEC Schedule, 12-17, Insurance Companies, Reinsurance [Line Items]
Remaining Reinsurance in Force	495,889
2019 | Other Reinsurance
SEC Schedule, 12-17, Insurance Companies, Reinsurance [Line Items]
Remaining Reinsurance in Force	55,102
2019 and 2020
SEC Schedule, 12-17, Insurance Companies, Reinsurance [Line Items]
Remaining Insurance in Force	39,400,549
Remaining Risk in Force	9,903,301
Remaining Reinsurance in Force	313,772
Remaining First Layer Retention	465,690
2019 and 2020 | Radnor Re 2020-2 Ltd.
SEC Schedule, 12-17, Insurance Companies, Reinsurance [Line Items]
Remaining Reinsurance in Force	313,772
2019 and 2020 | Other Reinsurance
SEC Schedule, 12-17, Insurance Companies, Reinsurance [Line Items]
Remaining Reinsurance in Force	0
2020 and 2021
SEC Schedule, 12-17, Insurance Companies, Reinsurance [Line Items]
Remaining Insurance in Force	56,303,818
Remaining Risk in Force	13,658,801
Remaining Reinsurance in Force	557,911
Remaining First Layer Retention	278,956
2020 and 2021 | Radnor Re 2021-1 Ltd.
SEC Schedule, 12-17, Insurance Companies, Reinsurance [Line Items]
Remaining Reinsurance in Force	557,911
2020 and 2021 | Other Reinsurance
SEC Schedule, 12-17, Insurance Companies, Reinsurance [Line Items]
Remaining Reinsurance in Force	$ 0