Investments Available for Sale (Details 4) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Realized gross gains and losses on the sale of investments available for sale
Realized gross gains	$ 2,822,000	$ 3,908,000	$ 1,368,000
Realized gross losses	788,000	1,073,000	443,000
Fair Value
Less than 12 months	877,394,000	633,959,000
12 months or more	77,782,000	66,780,000
Total	955,176,000	700,739,000
Gross Unrealized Losses
Less than 12 months	(20,789,000)	(7,212,000)
12 months or more	(777,000)	(1,661,000)
Total	(21,566,000)	(8,873,000)
Other information
Other-than-temporary impairments	100,000	300,000	$ 0
Fair value of investments deposited with insurance regulatory authorities	8,500,000	8,500,000
U.S. Treasury securities
Fair Value
Less than 12 months	160,018,000	110,699,000
12 months or more	0	0
Total	160,018,000	110,699,000
Gross Unrealized Losses
Less than 12 months	(4,497,000)	(1,088,000)
12 months or more	0	0
Total	(4,497,000)	(1,088,000)
Municipal debt securities
Fair Value
Less than 12 months	149,368,000	47,850,000
12 months or more	6,015,000	1,254,000
Total	155,383,000	49,104,000
Gross Unrealized Losses
Less than 12 months	(3,351,000)	(255,000)
12 months or more	(22,000)	(7,000)
Total	(3,373,000)	(262,000)
Corporate debt securities
Fair Value
Less than 12 months	213,965,000	252,792,000
12 months or more	8,344,000	9,404,000
Total	222,309,000	262,196,000
Gross Unrealized Losses
Less than 12 months	(3,704,000)	(3,447,000)
12 months or more	(124,000)	(405,000)
Total	(3,828,000)	(3,852,000)
Residential and commercial mortgage securities
Fair Value
Less than 12 months	18,026,000	23,360,000
12 months or more	14,014,000	26,075,000
Total	32,040,000	49,435,000
Gross Unrealized Losses
Less than 12 months	(434,000)	(458,000)
12 months or more	(148,000)	(663,000)
Total	(582,000)	(1,121,000)
Asset-backed securities
Fair Value
Less than 12 months	28,294,000	86,431,000
12 months or more	47,597,000	26,364,000
Total	75,891,000	112,795,000
Gross Unrealized Losses
Less than 12 months	(57,000)	(871,000)
12 months or more	(390,000)	(448,000)
Total	(447,000)	(1,319,000)
Essent Re
Other information
Fair value of the required investments on deposit in trusts	349,600,000	194,500,000
U.S. Agency | U.S. agency securities
Fair Value
Less than 12 months	18,441,000	11,362,000
12 months or more	0	0
Total	18,441,000	11,362,000
Gross Unrealized Losses
Less than 12 months	(344,000)	(178,000)
12 months or more	0	0
Total	(344,000)	(178,000)
U.S. Agency | U.S. agency mortgage-backed securities
Fair Value
Less than 12 months	289,282,000	101,465,000
12 months or more	1,812,000	3,683,000
Total	291,094,000	105,148,000
Gross Unrealized Losses
Less than 12 months	(8,402,000)	(915,000)
12 months or more	(93,000)	(138,000)
Total	$ (8,495,000)	$ (1,053,000)