Investments Available for Sale (Details 4) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016
Realized gross gains and losses on the sale of investments available for sale
Realized gross gains	$ 749,000	$ 624,000	$ 1,430,000	$ 1,772,000
Realized gross losses	205,000	$ 41,000	231,000	711,000
Fair Value
Less than 12 months	801,010,000		801,010,000		$ 877,394,000
12 months or more	34,416,000		34,416,000		77,782,000
Total	835,426,000		835,426,000		955,176,000
Gross Unrealized Losses
Less than 12 months	(12,190,000)		(12,190,000)		(20,789,000)
12 months or more	(243,000)		(243,000)		(777,000)
Total	(12,433,000)		(12,433,000)		(21,566,000)
Other information
Other-than-temporary impairments	0		0	$ 7,000
Fair value of investments deposited with insurance regulatory authorities	8,600,000		8,600,000		8,500,000
U.S. Treasury securities
Fair Value
Less than 12 months	162,420,000		162,420,000		160,018,000
12 months or more	0		0		0
Total	162,420,000		162,420,000		160,018,000
Gross Unrealized Losses
Less than 12 months	(2,746,000)		(2,746,000)		(4,497,000)
12 months or more	0		0		0
Total	(2,746,000)		(2,746,000)		(4,497,000)
Municipal debt securities
Fair Value
Less than 12 months	70,885,000		70,885,000		149,368,000
12 months or more	4,017,000		4,017,000		6,015,000
Total	74,902,000		74,902,000		155,383,000
Gross Unrealized Losses
Less than 12 months	(816,000)		(816,000)		(3,351,000)
12 months or more	(30,000)		(30,000)		(22,000)
Total	(846,000)		(846,000)		(3,373,000)
Corporate debt securities
Fair Value
Less than 12 months	192,204,000		192,204,000		213,965,000
12 months or more	7,564,000		7,564,000		8,344,000
Total	199,768,000		199,768,000		222,309,000
Gross Unrealized Losses
Less than 12 months	(1,943,000)		(1,943,000)		(3,704,000)
12 months or more	(26,000)		(26,000)		(124,000)
Total	(1,969,000)		(1,969,000)		(3,828,000)
Residential and commercial mortgage securities
Fair Value
Less than 12 months	12,218,000		12,218,000		18,026,000
12 months or more	1,547,000		1,547,000		14,014,000
Total	13,765,000		13,765,000		32,040,000
Gross Unrealized Losses
Less than 12 months	(264,000)		(264,000)		(434,000)
12 months or more	(9,000)		(9,000)		(148,000)
Total	(273,000)		(273,000)		(582,000)
Asset-backed securities
Fair Value
Less than 12 months	32,371,000		32,371,000		28,294,000
12 months or more	19,080,000		19,080,000		47,597,000
Total	51,451,000		51,451,000		75,891,000
Gross Unrealized Losses
Less than 12 months	(108,000)		(108,000)		(57,000)
12 months or more	(104,000)		(104,000)		(390,000)
Total	(212,000)		(212,000)		(447,000)
U.S. Agency | U.S. agency securities
Fair Value
Less than 12 months	20,232,000		20,232,000		18,441,000
12 months or more	0		0		0
Total	20,232,000		20,232,000		18,441,000
Gross Unrealized Losses
Less than 12 months	(250,000)		(250,000)		(344,000)
12 months or more	0		0		0
Total	(250,000)		(250,000)		(344,000)
U.S. Agency | U.S. agency mortgage-backed securities
Fair Value
Less than 12 months	310,680,000		310,680,000		289,282,000
12 months or more	2,208,000		2,208,000		1,812,000
Total	312,888,000		312,888,000		291,094,000
Gross Unrealized Losses
Less than 12 months	(6,063,000)		(6,063,000)		(8,402,000)
12 months or more	(74,000)		(74,000)		(93,000)
Total	(6,137,000)		(6,137,000)		(8,495,000)
Essent Re
Other information
Fair value of the required investments on deposit in trusts	$ 487,400,000		$ 487,400,000		$ 349,600,000