Investments In Fixed Maturity Securities Investments in Fixed Maturity Securities (Investments in fixed maturity securities) (Details) (USD $)	Mar. 31, 2014		Dec. 31, 2013
Schedule of Available-for-sale Securities [Line Items]
Total held to maturity, Amortized Cost	$ 101,335,000		$ 101,320,000
Held to Maturity Securities Accumulated Unrecognized Holding Gain	17,838,000		14,900,000
Held to Maturity Securities Accumulated Unrecognized Holding Loss	0		0
Total held to maturity, Fair Value	119,173,000		116,220,000
Total held to maturity, Carrying Value	101,335,000		101,320,000
Total available for sale, Amortized Cost	11,467,724,000		11,190,311,000
Total available for sale, Gross Unrealized Gains	492,987,000		436,347,000
Total available for sale, Gross Unrealized Losses	(75,569,000)		(111,134,000)
Total available for sale, Fair Value	11,885,142,000		11,515,524,000
Total available for sale, Carrying Value	11,885,142,000		11,515,524,000
Total investments in fixed maturity securities, Amortized Value	11,569,059,000		11,291,631,000
Total investments in fixed maturity securities, Gross Unrealized Gains	510,825,000		451,247,000
Total investments in fixed maturity securities, Gross Unrealized Losses	(75,569,000)		(111,134,000)
Total investments in fixed maturity securities, Fair Value	12,004,315,000		11,631,744,000
Total investments in fixed maturity securities, Carrying Value	11,986,477,000		11,616,844,000
Minimum ownership of Common stockholders equity	10.00%
Foreign government
Schedule of Available-for-sale Securities [Line Items]
Total available for sale, Amortized Cost	866,569,000		844,469,000
Total available for sale, Gross Unrealized Gains	59,665,000		51,674,000
Total available for sale, Gross Unrealized Losses	(15,088,000)		(16,286,000)
Total available for sale, Fair Value	911,146,000		879,857,000
Total available for sale, Carrying Value	911,146,000		879,857,000
Commercial Mortgage Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Total available for sale, Amortized Cost	65,077,000		76,454,000
Total available for sale, Gross Unrealized Gains	6,626,000		5,670,000
Total available for sale, Gross Unrealized Losses	(413,000)		(988,000)
Total available for sale, Fair Value	71,290,000		81,136,000
Total available for sale, Carrying Value	71,290,000		81,136,000
U.S. government and government agency
Schedule of Available-for-sale Securities [Line Items]
Total available for sale, Amortized Cost	905,005,000		858,319,000
Total available for sale, Gross Unrealized Gains	35,029,000		34,522,000
Total available for sale, Gross Unrealized Losses	(9,177,000)		(7,982,000)
Total available for sale, Fair Value	930,857,000		884,859,000
Total available for sale, Carrying Value	930,857,000		884,859,000
Residential Mortgage Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Total available for sale, Amortized Cost	1,270,514,000	[1]	1,248,693,000	[1]
Total available for sale, Gross Unrealized Gains	26,194,000	[1]	25,895,000	[1]
Total available for sale, Gross Unrealized Losses	(19,090,000)	[1]	(25,941,000)	[1]
Total available for sale, Fair Value	1,277,618,000	[1]	1,248,647,000	[1]
Total available for sale, Carrying Value	1,277,618,000	[1]	1,248,647,000	[1]
Non-credit portion of other-than-temporary impairments (OTTI)	1,402,000		1,961,000
Corporate Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Total available for sale, Amortized Cost	4,281,162,000		4,076,585,000
Total available for sale, Gross Unrealized Gains	176,594,000		156,256,000
Total available for sale, Gross Unrealized Losses	(20,557,000)		(30,100,000)
Total available for sale, Fair Value	4,437,199,000		4,202,741,000
Total available for sale, Carrying Value	4,437,199,000		4,202,741,000
State and municipal
Schedule of Available-for-sale Securities [Line Items]
Total available for sale, Amortized Cost	4,079,397,000		4,085,791,000
Total available for sale, Gross Unrealized Gains	188,879,000		162,330,000
Total available for sale, Gross Unrealized Losses	(11,244,000)		(29,837,000)
Total available for sale, Fair Value	4,257,032,000		4,218,284,000
Total available for sale, Carrying Value	4,257,032,000		4,218,284,000
State and municipal
Schedule of Available-for-sale Securities [Line Items]
Total held to maturity, Amortized Cost	69,928,000		68,929,000
Held to Maturity Securities Accumulated Unrecognized Holding Gain	14,266,000		11,172,000
Held to Maturity Securities Accumulated Unrecognized Holding Loss	0		0
Total held to maturity, Fair Value	84,194,000		80,101,000
Total held to maturity, Carrying Value	69,928,000		68,929,000
Residential Mortgage Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Total held to maturity, Amortized Cost	26,409,000		27,393,000
Held to Maturity Securities Accumulated Unrecognized Holding Gain	3,211,000		3,311,000
Held to Maturity Securities Accumulated Unrecognized Holding Loss	0		0
Total held to maturity, Fair Value	29,620,000		30,704,000
Total held to maturity, Carrying Value	26,409,000		27,393,000
Corporate Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Total held to maturity, Amortized Cost	4,998,000		4,998,000
Held to Maturity Securities Accumulated Unrecognized Holding Gain	361,000		417,000
Held to Maturity Securities Accumulated Unrecognized Holding Loss	0		0
Total held to maturity, Fair Value	5,359,000		5,415,000
Total held to maturity, Carrying Value	$ 4,998,000		$ 4,998,000

[1] Gross unrealized losses for residential mortgage-backed securities include $1,402,000 and $1,961,000 as of March 31, 2014 and December 31, 2013, respectively, related to the non-credit portion of other-than-temporary impairments (“OTTI”) recognized in accumulated other comprehensive income.