Investments Available for Sale (Details 4)	12 Months Ended
	Dec. 31, 2015 USD ($) security	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)
Realized gross gains and losses on the sale of investments available for sale
Realized gross gains	$ 3,908,000	$ 1,368,000	$ 116,000
Realized gross losses	1,073,000	443,000	0
Fair Value
Less than 12 months	633,959,000	300,835,000
12 months or more	66,780,000	53,357,000
Total	700,739,000	354,192,000
Gross Unrealized Losses
Less than 12 months	(7,212,000)	(1,633,000)
12 months or more	(1,661,000)	(1,155,000)
Total	$ (8,873,000)	(2,788,000)
Other information
Number of available-for-sale securities sold in unrealized loss positions | security	2
Other-than-temporary impairments	$ 300,000	0	$ 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	110,699,000	16,543,000
12 months or more		5,155,000
Total	110,699,000	21,698,000
Gross Unrealized Losses
Less than 12 months	(1,088,000)	(34,000)
12 months or more		(109,000)
Total	(1,088,000)	(143,000)
Municipal debt securities
Fair Value
Less than 12 months	47,850,000	39,902,000
12 months or more	1,254,000	8,684,000
Total	49,104,000	48,586,000
Gross Unrealized Losses
Less than 12 months	(255,000)	(229,000)
12 months or more	(7,000)	(95,000)
Total	(262,000)	(324,000)
Corporate debt securities
Fair Value
Less than 12 months	252,792,000	113,717,000
12 months or more	9,404,000	12,659,000
Total	262,196,000	126,376,000
Gross Unrealized Losses
Less than 12 months	(3,447,000)	(701,000)
12 months or more	(405,000)	(100,000)
Total	(3,852,000)	(801,000)
Mortgage-backed securities
Fair Value
Less than 12 months	23,360,000	28,091,000
12 months or more	26,075,000	16,092,000
Total	49,435,000	44,183,000
Gross Unrealized Losses
Less than 12 months	(458,000)	(264,000)
12 months or more	(663,000)	(620,000)
Total	(1,121,000)	(884,000)
Asset-backed securities
Fair Value
Less than 12 months	86,431,000	100,248,000
12 months or more	26,364,000	2,201,000
Total	112,795,000	102,449,000
Gross Unrealized Losses
Less than 12 months	(871,000)	(405,000)
12 months or more	(448,000)	(17,000)
Total	(1,319,000)	(422,000)
Essent Re
Other information
Fair value of the required investments on deposit in trusts	171,500,000	66,700,000
U.S. Agency | U.S. agency securities
Fair Value
Less than 12 months	11,362,000
Total	11,362,000
Gross Unrealized Losses
Less than 12 months	(178,000)
Total	(178,000)
U.S. Agency | U.S. agency mortgage-backed securities
Fair Value
Less than 12 months	101,465,000	2,334,000
12 months or more	3,683,000	8,566,000
Total	105,148,000	10,900,000
Gross Unrealized Losses
Less than 12 months	(915,000)
12 months or more	(138,000)	(214,000)
Total	$ (1,053,000)	$ (214,000)