Investments In Fixed Maturity Securities Investments in Fixed Maturity Securities (Investments in fixed maturity securities) (Details) - USD ($)		Jun. 30, 2015	Dec. 31, 2014
Schedule of Available-for-sale Securities [Line Items]
Total held to maturity, Amortized Cost		$ 101,306,000	$ 101,177,000
Held to Maturity Securities Accumulated Unrecognized Holding Gain		17,826,000	20,646,000
Held to Maturity Securities Accumulated Unrecognized Holding Loss		0	0
Total held to maturity, Fair Value		119,132,000	121,823,000
Total held to maturity, Carrying Value		101,306,000	101,177,000
Total available for sale, Amortized Cost		11,917,655,000	12,122,087,000
Total available for sale, Gross Unrealized Gains		457,432,000	541,420,000
Total available for sale, Gross Unrealized Losses		(80,583,000)	(59,524,000)
Total available for sale, Fair Value		12,294,504,000	12,603,983,000
Total available for sale, Carrying Value		12,294,504,000	12,603,983,000
Total investments in fixed maturity securities, Amortized Value		12,018,961,000	12,223,264,000
Total investments in fixed maturity securities, Gross Unrealized Gains		475,258,000	562,066,000
Total investments in fixed maturity securities, Gross Unrealized Losses		(80,583,000)	(59,524,000)
Total investments in fixed maturity securities, Fair Value		12,413,636,000	12,725,806,000
Total investments in fixed maturity securities, Carrying Value		$ 12,395,810,000	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		$ 918,738,000	897,668,000
Total available for sale, Gross Unrealized Gains		65,344,000	62,223,000
Total available for sale, Gross Unrealized Losses		(16,932,000)	(18,065,000)
Total available for sale, Fair Value		967,150,000	941,826,000
Total available for sale, Carrying Value		967,150,000	941,826,000
Commercial Mortgage Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Total available for sale, Amortized Cost		68,378,000	74,479,000
Total available for sale, Gross Unrealized Gains		1,053,000	1,610,000
Total available for sale, Gross Unrealized Losses		(93,000)	(52,000)
Total available for sale, Fair Value		69,338,000	76,037,000
Total available for sale, Carrying Value		69,338,000	76,037,000
U.S. government and government agency
Schedule of Available-for-sale Securities [Line Items]
Total available for sale, Amortized Cost		691,250,000	773,192,000
Total available for sale, Gross Unrealized Gains		27,672,000	33,353,000
Total available for sale, Gross Unrealized Losses		(3,555,000)	(3,157,000)
Total available for sale, Fair Value		715,367,000	803,388,000
Total available for sale, Carrying Value		715,367,000	803,388,000
Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Total available for sale, Amortized Cost		2,345,401,000	2,264,210,000
Total available for sale, Gross Unrealized Gains		91,768,000	111,841,000
Total available for sale, Gross Unrealized Losses		(8,386,000)	(2,084,000)
Total available for sale, Fair Value		2,428,783,000	2,373,967,000
Total available for sale, Carrying Value		2,428,783,000	2,373,967,000
Corporation [Member]
Schedule of Available-for-sale Securities [Line Items]
Total available for sale, Amortized Cost		419,572,000	413,234,000
Total available for sale, Gross Unrealized Gains		13,850,000	18,976,000
Total available for sale, Gross Unrealized Losses		(998,000)	(855,000)
Total available for sale, Fair Value		432,424,000	431,355,000
Total available for sale, Carrying Value		432,424,000	431,355,000
Debt, State Government [Member]
Schedule of Available-for-sale Securities [Line Items]
Total available for sale, Amortized Cost		640,845,000	674,022,000
Total available for sale, Gross Unrealized Gains		25,694,000	37,615,000
Total available for sale, Gross Unrealized Losses		(6,113,000)	(787,000)
Total available for sale, Fair Value		660,426,000	710,850,000
Total available for sale, Carrying Value		660,426,000	710,850,000
Revenue Subject to Refund [Member]
Schedule of Available-for-sale Securities [Line Items]
Total available for sale, Amortized Cost		444,165,000	504,778,000
Total available for sale, Gross Unrealized Gains		28,606,000	35,619,000
Total available for sale, Gross Unrealized Losses		(133,000)	(289,000)
Total available for sale, Fair Value		472,638,000	540,108,000
Total available for sale, Carrying Value		472,638,000	540,108,000
Residential Mortgage Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Total available for sale, Amortized Cost	[1]	1,085,961,000	1,201,924,000
Total available for sale, Gross Unrealized Gains	[1]	24,498,000	27,124,000
Total available for sale, Gross Unrealized Losses	[1]	(10,514,000)	(9,449,000)
Total available for sale, Fair Value	[1]	1,099,945,000	1,219,599,000
Total available for sale, Carrying Value	[1]	1,099,945,000	1,219,599,000
Non-credit portion of other-than-temporary impairments (OTTI)		1,073,002	1,095,671
Corporate Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Total available for sale, Amortized Cost		5,019,357,000	5,036,958,000
Total available for sale, Gross Unrealized Gains		157,924,000	187,960,000
Total available for sale, Gross Unrealized Losses		(33,428,000)	(24,781,000)
Total available for sale, Fair Value		5,143,853,000	5,200,137,000
Total available for sale, Carrying Value		5,143,853,000	5,200,137,000
State and municipal
Schedule of Available-for-sale Securities [Line Items]
Total available for sale, Amortized Cost		4,133,971,000	4,137,866,000
Total available for sale, Gross Unrealized Gains		180,941,000	229,150,000
Total available for sale, Gross Unrealized Losses		(16,061,000)	(4,020,000)
Total available for sale, Fair Value		4,298,851,000	4,362,996,000
Total available for sale, Carrying Value		4,298,851,000	4,362,996,000
Debt, Local Government [Member]
Schedule of Available-for-sale Securities [Line Items]
Total available for sale, Amortized Cost		283,988,000	281,622,000
Total available for sale, Gross Unrealized Gains		21,023,000	25,099,000
Total available for sale, Gross Unrealized Losses		(431,000)	(5,000)
Total available for sale, Fair Value		304,580,000	306,716,000
Total available for sale, Carrying Value		304,580,000	306,716,000
Mortgage-backed securities
Schedule of Available-for-sale Securities [Line Items]
Total available for sale, Amortized Cost		1,154,339,000	1,276,403,000
Total available for sale, Gross Unrealized Gains		25,551,000	28,734,000
Total available for sale, Gross Unrealized Losses		(10,607,000)	(9,501,000)
Total available for sale, Fair Value		1,169,283,000	1,295,636,000
Total available for sale, Carrying Value		1,169,283,000	1,295,636,000
Asset-backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Total available for sale, Amortized Cost		1,644,366,000	2,019,032,000
Total available for sale, Gross Unrealized Gains		17,816,000	18,868,000
Total available for sale, Gross Unrealized Losses		(10,027,000)	(11,974,000)
Total available for sale, Fair Value		1,652,155,000	2,025,926,000
Total available for sale, Carrying Value		1,652,155,000	2,025,926,000
Industrial Property [Member]
Schedule of Available-for-sale Securities [Line Items]
Total available for sale, Amortized Cost		1,780,193,000	1,606,724,000
Total available for sale, Gross Unrealized Gains		96,890,000	117,206,000
Total available for sale, Gross Unrealized Losses		(10,238,000)	(5,131,000)
Total available for sale, Fair Value		1,866,845,000	1,718,799,000
Total available for sale, Carrying Value		1,866,845,000	1,718,799,000
Domestic Corporate Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Total available for sale, Amortized Cost		1,296,370,000	1,140,801,000
Total available for sale, Gross Unrealized Gains		32,050,000	38,080,000
Total available for sale, Gross Unrealized Losses		(10,412,000)	(7,673,000)
Total available for sale, Fair Value		1,318,008,000	1,171,208,000
Total available for sale, Carrying Value		1,318,008,000	1,171,208,000
Public Utility, Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Total available for sale, Amortized Cost		182,282,000	184,107,000
Total available for sale, Gross Unrealized Gains		10,412,000	12,436,000
Total available for sale, Gross Unrealized Losses		(2,212,000)	(1,000)
Total available for sale, Fair Value		190,482,000	196,542,000
Total available for sale, Carrying Value		190,482,000	196,542,000
Other Security Investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Total available for sale, Amortized Cost		116,146,000	86,294,000
Total available for sale, Gross Unrealized Gains		756,000	1,370,000
Total available for sale, Gross Unrealized Losses		(539,000)	(2,000)
Total available for sale, Fair Value		116,363,000	87,662,000
Total available for sale, Carrying Value		116,363,000	87,662,000
State and municipal
Schedule of Available-for-sale Securities [Line Items]
Total held to maturity, Amortized Cost		75,066,000	72,901,000
Held to Maturity Securities Accumulated Unrecognized Holding Gain		15,029,000	17,501,000
Held to Maturity Securities Accumulated Unrecognized Holding Loss		0	0
Total held to maturity, Fair Value		90,095,000	90,402,000
Total held to maturity, Carrying Value		75,066,000	72,901,000
Residential Mortgage Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Total held to maturity, Amortized Cost		21,241,000	23,278,000
Held to Maturity Securities Accumulated Unrecognized Holding Gain		2,655,000	2,854,000
Held to Maturity Securities Accumulated Unrecognized Holding Loss		0	0
Total held to maturity, Fair Value		23,896,000	26,132,000
Total held to maturity, Carrying Value		21,241,000	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		142,000	291,000
Held to Maturity Securities Accumulated Unrecognized Holding Loss		0	0
Total held to maturity, Fair Value		5,141,000	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 $1,073,002 and $1,095,671 as of June 30, 2015 and December 31, 2014, respectively, related to the non-credit portion of other-than-temporary impairments (“OTTI”) recognized in accumulated other comprehensive income.