Investments (Details 1) (USD $) In Thousands, unless otherwise specified	3 Months Ended	12 Months Ended
	Mar. 31, 2014	Dec. 31, 2013
Gross unrealized losses and fair value of all available for sale fixed maturity securities that were in a continuous loss position
Less than 12 months, Fair value	$ 1,564,101	$ 1,913,235
Less than 12 months, Unrealized losses	(48,987)	(85,659)
12 months or more, Fair value	211,447	171,280
12 months or more, Unrealized losses	(13,852)	(19,562)
Total, Fair value	1,775,548	2,084,515
Total, Unrealized losses	(62,839)	(105,221)
US Government and Government Agency Securities [Member]
Gross unrealized losses and fair value of all available for sale fixed maturity securities that were in a continuous loss position
Less than 12 months, Fair value	25,035	23,717
Less than 12 months, Unrealized losses	(400)	(495)
12 months or more, Fair value	0	0
12 months or more, Unrealized losses	0	0
Total, Fair value	25,035	23,717
Total, Unrealized losses	(400)	(495)
Fixed Maturity Securities of States, Municipalities and Political Subdivisions Securities [Member]
Gross unrealized losses and fair value of all available for sale fixed maturity securities that were in a continuous loss position
Less than 12 months, Fair value	76,962	136,160
Less than 12 months, Unrealized losses	(1,924)	(5,277)
12 months or more, Fair value	9,219	8,997
12 months or more, Unrealized losses	(437)	(702)
Total, Fair value	86,181	145,157
Total, Unrealized losses	(2,361)	(5,979)
Special Purpose Revenue Bonds Of States Municipalities And Political Subdivisions [Member]
Gross unrealized losses and fair value of all available for sale fixed maturity securities that were in a continuous loss position
Less than 12 months, Fair value	472,150	684,560
Less than 12 months, Unrealized losses	(14,315)	(35,832)
12 months or more, Fair value	102,936	83,228
12 months or more, Unrealized losses	(5,892)	(10,926)
Total, Fair value	575,086	767,788
Total, Unrealized losses	(20,207)	(46,758)
Corporate Securities [Member]
Gross unrealized losses and fair value of all available for sale fixed maturity securities that were in a continuous loss position
Less than 12 months, Fair value	247,972	277,853
Less than 12 months, Unrealized losses	(5,160)	(8,202)
12 months or more, Fair value	36,873	35,437
12 months or more, Unrealized losses	(1,757)	(2,807)
Total, Fair value	284,845	313,290
Total, Unrealized losses	(6,917)	(11,009)
Residential Mortgage Backed Securities [Member]
Gross unrealized losses and fair value of all available for sale fixed maturity securities that were in a continuous loss position
Less than 12 months, Fair value	283,429	306,874
Less than 12 months, Unrealized losses	(10,749)	(15,861)
12 months or more, Fair value	41,796	31,687
12 months or more, Unrealized losses	(4,144)	(4,075)
Total, Fair value	325,225	338,561
Total, Unrealized losses	(14,893)	(19,936)
Commercial Mortgage Backed Securities [Member]
Gross unrealized losses and fair value of all available for sale fixed maturity securities that were in a continuous loss position
Less than 12 months, Fair value	171,448	203,347
Less than 12 months, Unrealized losses	(7,196)	(12,611)
12 months or more, Fair value	20,371	4,915
12 months or more, Unrealized losses	(1,612)	(725)
Total, Fair value	191,819	208,262
Total, Unrealized losses	(8,808)	(13,336)
Asset-backed Securities [Member]
Gross unrealized losses and fair value of all available for sale fixed maturity securities that were in a continuous loss position
Less than 12 months, Fair value	158,396	126,922
Less than 12 months, Unrealized losses	(1,576)	(1,587)
12 months or more, Fair value	0	0
12 months or more, Unrealized losses	0	0
Total, Fair value	158,396	126,922
Total, Unrealized losses	(1,576)	(1,587)
Foreign Government Securities [Member]
Gross unrealized losses and fair value of all available for sale fixed maturity securities that were in a continuous loss position
Less than 12 months, Fair value	29,280	78,182
Less than 12 months, Unrealized losses	(208)	(357)
12 months or more, Fair value	0	0
12 months or more, Unrealized losses	0	0
Total, Fair value	29,280	78,182
Total, Unrealized losses	(208)	(357)
Equity Securities [Member]
Gross unrealized losses and fair value of all available for sale fixed maturity securities that were in a continuous loss position
Less than 12 months, Fair value	99,429	75,620
Less than 12 months, Unrealized losses	(7,459)	(5,437)
12 months or more, Fair value	252	7,016
12 months or more, Unrealized losses	(10)	(327)
Total, Fair value	99,681	82,636
Total, Unrealized losses	$ (7,469)	$ (5,764)