Investments - Summary of Realized Gain and Loss and Investments in Unrealized Loss Position (Details)	12 Months Ended
	Dec. 31, 2019 USD ($) security	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Debt Securities, Available-for-sale [Line Items]
Realized gross gains	$ 5,238,000	$ 2,201,000	$ 2,504,000
Realized gross losses	1,746,000	883,000	425,000
Fair Value
Less than 12 months	372,179,000	930,556,000
12 months or more	310,585,000	918,818,000
Total	682,764,000	1,849,374,000
Gross Unrealized Losses
Less than 12 months	(3,369,000)	(14,097,000)
12 months or more	(2,700,000)	(30,033,000)
Total	$ (6,069,000)	(44,130,000)
Other Information
Number of investment securities in unrealized loss position | security	365
Other-than-temporary impairment	$ 300,000	0	$ 100,000
Other invested assets	78,873,000	30,952,000
Fair value of investments deposited with insurance regulatory authorities to meet statutory requirements	9,400,000	8,900,000
U.S. Treasury securities
Fair Value
Less than 12 months	29,013,000	45,505,000
12 months or more	42,981,000	165,015,000
Total	71,994,000	210,520,000
Gross Unrealized Losses
Less than 12 months	(331,000)	(215,000)
12 months or more	(76,000)	(5,731,000)
Total	(407,000)	(5,946,000)
U.S. agency securities
Fair Value
Less than 12 months	0	0
12 months or more	25,605,000	32,997,000
Total	25,605,000	32,997,000
Gross Unrealized Losses
Less than 12 months	0	0
12 months or more	(51,000)	(648,000)
Total	(51,000)	(648,000)
U.S. agency mortgage-backed securities
Fair Value
Less than 12 months	101,684,000	106,177,000
12 months or more	113,866,000	341,579,000
Total	215,550,000	447,756,000
Gross Unrealized Losses
Less than 12 months	(1,042,000)	(1,070,000)
12 months or more	(1,290,000)	(13,500,000)
Total	(2,332,000)	(14,570,000)
Municipal debt securities
Fair Value
Less than 12 months	10,651,000	114,442,000
12 months or more	624,000	104,930,000
Total	11,275,000	219,372,000
Gross Unrealized Losses
Less than 12 months	(112,000)	(1,176,000)
12 months or more	(6,000)	(1,843,000)
Total	(118,000)	(3,019,000)
Non-U.S. government securities
Fair Value
Less than 12 months	9,664,000	13,497,000
12 months or more	0	0
Total	9,664,000	13,497,000
Gross Unrealized Losses
Less than 12 months	(47,000)	(283,000)
12 months or more	0	0
Total	(47,000)	(283,000)
Corporate debt securities
Fair Value
Less than 12 months	83,013,000	381,912,000
12 months or more	14,531,000	231,124,000
Total	97,544,000	613,036,000
Gross Unrealized Losses
Less than 12 months	(576,000)	(7,538,000)
12 months or more	(16,000)	(7,230,000)
Total	(592,000)	(14,768,000)
Residential and commercial mortgage securities
Fair Value
Less than 12 months	59,341,000	51,477,000
12 months or more	3,442,000	13,321,000
Total	62,783,000	64,798,000
Gross Unrealized Losses
Less than 12 months	(1,059,000)	(650,000)
12 months or more	(42,000)	(567,000)
Total	(1,101,000)	(1,217,000)
Asset-backed securities
Fair Value
Less than 12 months	78,813,000	217,546,000
12 months or more	109,536,000	29,852,000
Total	188,349,000	247,398,000
Gross Unrealized Losses
Less than 12 months	(202,000)	(3,165,000)
12 months or more	(1,219,000)	(514,000)
Total	(1,421,000)	(3,679,000)
Essent Re
Other Information
Fair value of the required investments on deposit in trusts	805,500,000	759,900,000
Essent Guaranty
Other Information
Assets on deposit under reinsurance agreement	6,400,000	3,400,000
Assets on deposit for the benefit of the sponsor	$ 6,400,000	$ 6,300,000