Investments Available for Sale (Details 4) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016
Realized gross gains and losses on the sale of investments available for sale
Realized gross gains	$ 681	$ 1,148
Realized gross losses	26	670
Fair Value
Less than 12 months	834,848		$ 877,394
12 months or more	49,314		77,782
Total	884,162		955,176
Gross Unrealized Losses
Less than 12 months	(17,595)		(20,789)
12 months or more	(324)		(777)
Total	(17,919)		(21,566)
Other information
Other-than-temporary impairments		$ 7
Fair value of investments deposited with insurance regulatory authorities	8,500		8,500
U.S. Treasury securities
Fair Value
Less than 12 months	141,980		160,018
12 months or more	0		0
Total	141,980		160,018
Gross Unrealized Losses
Less than 12 months	(3,843)		(4,497)
12 months or more	0		0
Total	(3,843)		(4,497)
Municipal debt securities
Fair Value
Less than 12 months	116,284		149,368
12 months or more	6,651		6,015
Total	122,935		155,383
Gross Unrealized Losses
Less than 12 months	(2,124)		(3,351)
12 months or more	(32)		(22)
Total	(2,156)		(3,373)
Corporate debt securities
Fair Value
Less than 12 months	187,801		213,965
12 months or more	6,098		8,344
Total	193,899		222,309
Gross Unrealized Losses
Less than 12 months	(2,924)		(3,704)
12 months or more	(46)		(124)
Total	(2,970)		(3,828)
Residential and commercial mortgage securities
Fair Value
Less than 12 months	13,822		18,026
12 months or more	5,930		14,014
Total	19,752		32,040
Gross Unrealized Losses
Less than 12 months	(391)		(434)
12 months or more	(30)		(148)
Total	(421)		(582)
Asset-backed securities
Fair Value
Less than 12 months	41,891		28,294
12 months or more	28,855		47,597
Total	70,746		75,891
Gross Unrealized Losses
Less than 12 months	(286)		(57)
12 months or more	(132)		(390)
Total	(418)		(447)
U.S. Agency | U.S. agency securities
Fair Value
Less than 12 months	26,284		18,441
12 months or more	0		0
Total	26,284		18,441
Gross Unrealized Losses
Less than 12 months	(323)		(344)
12 months or more	0		0
Total	(323)		(344)
U.S. Agency | U.S. agency mortgage-backed securities
Fair Value
Less than 12 months	306,786		289,282
12 months or more	1,780		1,812
Total	308,566		291,094
Gross Unrealized Losses
Less than 12 months	(7,704)		(8,402)
12 months or more	(84)		(93)
Total	(7,788)		(8,495)
Essent Re
Other information
Fair value of the required investments on deposit in trusts	$ 406,900		$ 349,600