Investments In Fixed Maturity Securities Investments in Fixed Maturity Securities (Investments in fixed maturity securities) (Details) (USD $)	Mar. 31, 2015		Dec. 31, 2014
Schedule of Available-for-sale Securities [Line Items]
Total held to maturity, Amortized Cost	$ 101,273,000		$ 101,177,000
Held to Maturity Securities Accumulated Unrecognized Holding Gain	21,084,000		20,646,000
Held to Maturity Securities Accumulated Unrecognized Holding Loss	0		0
Total held to maturity, Fair Value	122,357,000		121,823,000
Total held to maturity, Carrying Value	101,273,000		101,177,000
Total available for sale, Amortized Cost	12,026,660,000		12,122,087,000
Total available for sale, Gross Unrealized Gains	575,281,000		541,420,000
Total available for sale, Gross Unrealized Losses	(50,945,000)		(59,524,000)
Total available for sale, Fair Value	12,550,996,000		12,603,983,000
Total available for sale, Carrying Value	12,550,996,000		12,603,983,000
Total investments in fixed maturity securities, Amortized Value	12,127,933,000		12,223,264,000
Total investments in fixed maturity securities, Gross Unrealized Gains	596,365,000		562,066,000
Total investments in fixed maturity securities, Gross Unrealized Losses	(50,945,000)		(59,524,000)
Total investments in fixed maturity securities, Fair Value	12,673,353,000		12,725,806,000
Total investments in fixed maturity securities, Carrying Value	12,652,269,000		12,705,160,000
Minimum ownership of Common stockholders equity	10.00%
Foreign government
Schedule of Available-for-sale Securities [Line Items]
Total available for sale, Amortized Cost	892,006,000		897,668,000
Total available for sale, Gross Unrealized Gains	64,854,000		62,223,000
Total available for sale, Gross Unrealized Losses	(18,141,000)		(18,065,000)
Total available for sale, Fair Value	938,719,000		941,826,000
Total available for sale, Carrying Value	938,719,000		941,826,000
Commercial Mortgage Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Total available for sale, Amortized Cost	71,083,000		74,479,000
Total available for sale, Gross Unrealized Gains	1,867,000		1,610,000
Total available for sale, Gross Unrealized Losses	(66,000)		(52,000)
Total available for sale, Fair Value	72,884,000		76,037,000
Total available for sale, Carrying Value	72,884,000		76,037,000
U.S. government and government agency
Schedule of Available-for-sale Securities [Line Items]
Total available for sale, Amortized Cost	719,947,000		773,192,000
Total available for sale, Gross Unrealized Gains	34,349,000		33,353,000
Total available for sale, Gross Unrealized Losses	(1,829,000)		(3,157,000)
Total available for sale, Fair Value	752,467,000		803,388,000
Total available for sale, Carrying Value	752,467,000		803,388,000
Residential Mortgage Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Total available for sale, Amortized Cost	1,100,122,000	[1]	1,201,924,000	[1]
Total available for sale, Gross Unrealized Gains	32,147,000	[1]	27,124,000	[1]
Total available for sale, Gross Unrealized Losses	(6,687,000)	[1]	(9,449,000)	[1]
Total available for sale, Fair Value	1,125,582,000	[1]	1,219,599,000	[1]
Total available for sale, Carrying Value	1,125,582,000	[1]	1,219,599,000	[1]
Non-credit portion of other-than-temporary impairments (OTTI)	1,088,067		1,095,671
Corporate Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Total available for sale, Amortized Cost	5,022,705,000		5,036,958,000
Total available for sale, Gross Unrealized Gains	209,711,000		187,960,000
Total available for sale, Gross Unrealized Losses	(19,776,000)		(24,781,000)
Total available for sale, Fair Value	5,212,640,000		5,200,137,000
Total available for sale, Carrying Value	5,212,640,000		5,200,137,000
State and municipal
Schedule of Available-for-sale Securities [Line Items]
Total available for sale, Amortized Cost	4,220,797,000		4,137,866,000
Total available for sale, Gross Unrealized Gains	232,353,000		229,150,000
Total available for sale, Gross Unrealized Losses	(4,446,000)		(4,020,000)
Total available for sale, Fair Value	4,448,704,000		4,362,996,000
Total available for sale, Carrying Value	4,448,704,000		4,362,996,000
State and municipal
Schedule of Available-for-sale Securities [Line Items]
Total held to maturity, Amortized Cost	73,974,000		72,901,000
Held to Maturity Securities Accumulated Unrecognized Holding Gain	17,820,000		17,501,000
Held to Maturity Securities Accumulated Unrecognized Holding Loss	0		0
Total held to maturity, Fair Value	91,794,000		90,402,000
Total held to maturity, Carrying Value	73,974,000		72,901,000
Residential Mortgage Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Total held to maturity, Amortized Cost	22,300,000		23,278,000
Held to Maturity Securities Accumulated Unrecognized Holding Gain	3,049,000		2,854,000
Held to Maturity Securities Accumulated Unrecognized Holding Loss	0		0
Total held to maturity, Fair Value	25,349,000		26,132,000
Total held to maturity, Carrying Value	22,300,000		23,278,000
Corporate Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Total held to maturity, Amortized Cost	4,999,000		4,998,000
Held to Maturity Securities Accumulated Unrecognized Holding Gain	215,000		291,000
Held to Maturity Securities Accumulated Unrecognized Holding Loss	0		0
Total held to maturity, Fair Value	5,214,000		5,289,000
Total held to maturity, Carrying Value	$ 4,999,000		$ 4,998,000

[1] Gross unrealized losses for residential mortgage-backed securities include $1,088,067 and $1,095,671 as of March 31, 2015 and December 31, 2014, respectively, related to the non-credit portion of other-than-temporary impairments (“OTTI”) recognized in accumulated other comprehensive income.