Income Taxes - Essent Holdings Income Taxes and Unrecognized Tax Benefits (Details) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Operating Loss Carryforwards [Line Items]
Unrecognized tax benefits	$ 0	$ 0
U.S.
Operating Loss Carryforwards [Line Items]
Taxes provided on un-remitted earnings	0
Cumulative amount of earnings that would be subject to withholding tax, if distributed outside of the U.S.	2,100,000,000
United States Ireland Tax Treaty Benefits Availed | U.S.
Operating Loss Carryforwards [Line Items]
Associated withholding tax liability on cumulative amount of earnings that would be subject to withholding tax, if distributed outside of the U.S.	103,500,000
Essent Holdings | Essent Irish Intermediate
Operating Loss Carryforwards [Line Items]
Withholding taxes accrued with respect to un-remitted earnings	$ 0
Essent Holdings | United States Ireland Tax Treaty Benefits Availed | Essent Irish Intermediate
Operating Loss Carryforwards [Line Items]
Withholding tax rate on dividends paid	5.00%
Essent Holdings | Absent Benefits Of United States Ireland Tax Treaty | Essent Irish Intermediate
Operating Loss Carryforwards [Line Items]
Withholding tax rate on dividends paid	30.00%