Investments In Fixed Maturity Securities Investments in Fixed Maturity Securities (Investments in fixed maturity securities) (Details) - USD ($)		Sep. 30, 2015	Dec. 31, 2014
Schedule of Available-for-sale Securities [Line Items]
Total held to maturity, Amortized Cost		$ 101,090,000	$ 101,177,000
Held to Maturity Securities Accumulated Unrecognized Holding Gain		18,526,000	20,646,000
Held to Maturity Securities Accumulated Unrecognized Holding Loss		0	0
Total held to maturity, Fair Value		119,616,000	121,823,000
Total held to maturity, Carrying Value		101,090,000	101,177,000
Total available for sale, Amortized Cost		11,886,732,000	12,122,087,000
Total available for sale, Gross Unrealized Gains		457,919,000	541,420,000
Total available for sale, Gross Unrealized Losses		(77,422,000)	(59,524,000)
Total available for sale, Fair Value		12,267,229,000	12,603,983,000
Total available for sale, Carrying Value		12,267,229,000	12,603,983,000
Total investments in fixed maturity securities, Amortized Value		11,987,822,000	12,223,264,000
Total investments in fixed maturity securities, Gross Unrealized Gains		476,445,000	562,066,000
Total investments in fixed maturity securities, Gross Unrealized Losses		(77,422,000)	(59,524,000)
Total investments in fixed maturity securities, Fair Value		12,386,845,000	12,725,806,000
Total investments in fixed maturity securities, Carrying Value		$ 12,368,319,000	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		$ 854,313,000	897,668,000
Total available for sale, Gross Unrealized Gains		46,433,000	62,223,000
Total available for sale, Gross Unrealized Losses		(16,077,000)	(18,065,000)
Total available for sale, Fair Value		884,669,000	941,826,000
Total available for sale, Carrying Value		884,669,000	941,826,000
Commercial Mortgage Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Total available for sale, Amortized Cost		67,003,000	74,479,000
Total available for sale, Gross Unrealized Gains		1,236,000	1,610,000
Total available for sale, Gross Unrealized Losses		(35,000)	(52,000)
Total available for sale, Fair Value		68,204,000	76,037,000
Total available for sale, Carrying Value		68,204,000	76,037,000
U.S. government and government agency
Schedule of Available-for-sale Securities [Line Items]
Total available for sale, Amortized Cost		641,696,000	773,192,000
Total available for sale, Gross Unrealized Gains		32,748,000	33,353,000
Total available for sale, Gross Unrealized Losses		(1,476,000)	(3,157,000)
Total available for sale, Fair Value		672,968,000	803,388,000
Total available for sale, Carrying Value		672,968,000	803,388,000
Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Total available for sale, Amortized Cost		2,476,539,000	2,264,210,000
Total available for sale, Gross Unrealized Gains		104,030,000	111,841,000
Total available for sale, Gross Unrealized Losses		(4,848,000)	(2,084,000)
Total available for sale, Fair Value		2,575,721,000	2,373,967,000
Total available for sale, Carrying Value		2,575,721,000	2,373,967,000
Corporation [Member]
Schedule of Available-for-sale Securities [Line Items]
Total available for sale, Amortized Cost		385,972,000	413,234,000
Total available for sale, Gross Unrealized Gains		13,156,000	18,976,000
Total available for sale, Gross Unrealized Losses		(709,000)	(855,000)
Total available for sale, Fair Value		398,419,000	431,355,000
Total available for sale, Carrying Value		398,419,000	431,355,000
Debt, State Government [Member]
Schedule of Available-for-sale Securities [Line Items]
Total available for sale, Amortized Cost		602,995,000	674,022,000
Total available for sale, Gross Unrealized Gains		28,828,000	37,615,000
Total available for sale, Gross Unrealized Losses		(4,511,000)	(787,000)
Total available for sale, Fair Value		627,312,000	710,850,000
Total available for sale, Carrying Value		627,312,000	710,850,000
Revenue Subject to Refund [Member]
Schedule of Available-for-sale Securities [Line Items]
Total available for sale, Amortized Cost		442,026,000	504,778,000
Total available for sale, Gross Unrealized Gains		34,132,000	35,619,000
Total available for sale, Gross Unrealized Losses		0	(289,000)
Total available for sale, Fair Value		476,158,000	540,108,000
Total available for sale, Carrying Value		476,158,000	540,108,000
Residential Mortgage Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Total available for sale, Amortized Cost	[1]	1,038,903,000	1,201,924,000
Total available for sale, Gross Unrealized Gains	[1]	27,601,000	27,124,000
Total available for sale, Gross Unrealized Losses	[1]	(7,084,000)	(9,449,000)
Total available for sale, Fair Value	[1]	1,059,420,000	1,219,599,000
Total available for sale, Carrying Value	[1]	1,059,420,000	1,219,599,000
Non-credit portion of other-than-temporary impairments (OTTI)		1,023,313	1,095,671
Corporate Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Total available for sale, Amortized Cost		5,055,909,000	5,036,958,000
Total available for sale, Gross Unrealized Gains		144,787,000	187,960,000
Total available for sale, Gross Unrealized Losses		(42,485,000)	(24,781,000)
Total available for sale, Fair Value		5,158,211,000	5,200,137,000
Total available for sale, Carrying Value		5,158,211,000	5,200,137,000
State and municipal
Schedule of Available-for-sale Securities [Line Items]
Total available for sale, Amortized Cost		4,228,908,000	4,137,866,000
Total available for sale, Gross Unrealized Gains		205,114,000	229,150,000
Total available for sale, Gross Unrealized Losses		(10,265,000)	(4,020,000)
Total available for sale, Fair Value		4,423,757,000	4,362,996,000
Total available for sale, Carrying Value		4,423,757,000	4,362,996,000
Debt, Local Government [Member]
Schedule of Available-for-sale Securities [Line Items]
Total available for sale, Amortized Cost		321,376,000	281,622,000
Total available for sale, Gross Unrealized Gains		24,968,000	25,099,000
Total available for sale, Gross Unrealized Losses		(197,000)	(5,000)
Total available for sale, Fair Value		346,147,000	306,716,000
Total available for sale, Carrying Value		346,147,000	306,716,000
Mortgage-backed securities
Schedule of Available-for-sale Securities [Line Items]
Total available for sale, Amortized Cost		1,105,906,000	1,276,403,000
Total available for sale, Gross Unrealized Gains		28,837,000	28,734,000
Total available for sale, Gross Unrealized Losses		(7,119,000)	(9,501,000)
Total available for sale, Fair Value		1,127,624,000	1,295,636,000
Total available for sale, Carrying Value		1,127,624,000	1,295,636,000
Asset-backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Total available for sale, Amortized Cost		1,634,056,000	2,019,032,000
Total available for sale, Gross Unrealized Gains		17,722,000	18,868,000
Total available for sale, Gross Unrealized Losses		(11,681,000)	(11,974,000)
Total available for sale, Fair Value		1,640,097,000	2,025,926,000
Total available for sale, Carrying Value		1,640,097,000	2,025,926,000
Industrial Property [Member]
Schedule of Available-for-sale Securities [Line Items]
Total available for sale, Amortized Cost		1,888,762,000	1,606,724,000
Total available for sale, Gross Unrealized Gains		80,342,000	117,206,000
Total available for sale, Gross Unrealized Losses		(17,257,000)	(5,131,000)
Total available for sale, Fair Value		1,951,847,000	1,718,799,000
Total available for sale, Carrying Value		1,951,847,000	1,718,799,000
Domestic Corporate Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Total available for sale, Amortized Cost		1,264,970,000	1,140,801,000
Total available for sale, Gross Unrealized Gains		35,728,000	38,080,000
Total available for sale, Gross Unrealized Losses		(11,980,000)	(7,673,000)
Total available for sale, Fair Value		1,288,718,000	1,171,208,000
Total available for sale, Carrying Value		1,288,718,000	1,171,208,000
Public Utility, Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Total available for sale, Amortized Cost		187,325,000	184,107,000
Total available for sale, Gross Unrealized Gains		10,549,000	12,436,000
Total available for sale, Gross Unrealized Losses		(1,549,000)	(1,000)
Total available for sale, Fair Value		196,325,000	196,542,000
Total available for sale, Carrying Value		196,325,000	196,542,000
Other Security Investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Total available for sale, Amortized Cost		80,796,000	86,294,000
Total available for sale, Gross Unrealized Gains		446,000	1,370,000
Total available for sale, Gross Unrealized Losses		(18,000)	(2,000)
Total available for sale, Fair Value		81,224,000	87,662,000
Total available for sale, Carrying Value		81,224,000	87,662,000
State and municipal
Schedule of Available-for-sale Securities [Line Items]
Total held to maturity, Amortized Cost		76,065,000	72,901,000
Held to Maturity Securities Accumulated Unrecognized Holding Gain		15,824,000	17,501,000
Held to Maturity Securities Accumulated Unrecognized Holding Loss		0	0
Total held to maturity, Fair Value		91,889,000	90,402,000
Total held to maturity, Carrying Value		76,065,000	72,901,000
Residential Mortgage Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Total held to maturity, Amortized Cost		20,025,000	23,278,000
Held to Maturity Securities Accumulated Unrecognized Holding Gain		2,637,000	2,854,000
Held to Maturity Securities Accumulated Unrecognized Holding Loss		0	0
Total held to maturity, Fair Value		22,662,000	26,132,000
Total held to maturity, Carrying Value		20,025,000	23,278,000
Corporate Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Total held to maturity, Amortized Cost		5,000,000	4,998,000
Held to Maturity Securities Accumulated Unrecognized Holding Gain		65,000	291,000
Held to Maturity Securities Accumulated Unrecognized Holding Loss		0	0
Total held to maturity, Fair Value		5,065,000	5,289,000
Total held to maturity, Carrying Value		$ 5,000,000	$ 4,998,000

[1] Gross unrealized losses for residential mortgage-backed securities include $1,023,313 and $1,095,671 as of September 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.