Investments (Details 8) (USD $)	Dec. 31, 2012	Dec. 31, 2011
Fixed Maturities [Member]
Estimated Fair Values And Gross Unrealized Losses OTTI Impairment Losses Reported In AOCI [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	$ 1,445,262,000	$ 1,581,692,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses	22,324,000	73,831,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	414,211,000	667,783,000
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses	109,930,000	208,135,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	1,859,473,000	2,249,475,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses	132,254,000	281,966,000
Equity Securities [Member]
Estimated Fair Values And Gross Unrealized Losses OTTI Impairment Losses Reported In AOCI [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	90,951,000	21,178,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses	1,186,000	5,080,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	5,679,000	21,599,000
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses	118,000	5,440,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	96,630,000	42,777,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses	1,304,000	10,520,000
External Credit Rating, Investment Grade [Member] | Fixed Maturities [Member]
Estimated Fair Values And Gross Unrealized Losses OTTI Impairment Losses Reported In AOCI [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	1,242,157,000	1,304,417,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses	18,284,000	53,879,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	272,112,000	526,382,000
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses	42,960,000	128,295,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	1,514,269,000	1,830,799,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses	61,244,000	182,174,000
External Credit Rating, Non Investment Grade [Member] | Fixed Maturities [Member]
Estimated Fair Values And Gross Unrealized Losses OTTI Impairment Losses Reported In AOCI [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	203,105,000	277,275,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses	4,040,000	19,952,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	142,099,000	141,401,000
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses	66,970,000	79,840,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	345,204,000	418,676,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses	71,010,000	99,792,000
Corporate Debt Securities [Member] | External Credit Rating, Investment Grade [Member] | Fixed Maturities [Member]
Estimated Fair Values And Gross Unrealized Losses OTTI Impairment Losses Reported In AOCI [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	786,203,000	790,758,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses	13,276,000	40,180,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	108,187,000	286,244,000
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses	17,386,000	63,117,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	894,390,000	1,077,002,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses	30,662,000	103,297,000
Corporate Debt Securities [Member] | External Credit Rating, Non Investment Grade [Member] | Fixed Maturities [Member]
Estimated Fair Values And Gross Unrealized Losses OTTI Impairment Losses Reported In AOCI [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	181,168,000	212,795,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses	3,170,000	10,852,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	39,123,000	47,310,000
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses	5,501,000	11,222,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	220,291,000	260,105,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses	8,671,000	22,074,000
US Government Agencies Debt Securities [Member] | External Credit Rating, Investment Grade [Member] | Fixed Maturities [Member]
Estimated Fair Values And Gross Unrealized Losses OTTI Impairment Losses Reported In AOCI [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	7,272,000	1,764,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses	24,000	61,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	0	0
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses	0	0
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	7,272,000	1,764,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses	24,000	61,000
US States and Political Subdivisions Debt Securities [Member] | External Credit Rating, Investment Grade [Member] | Fixed Maturities [Member]
Estimated Fair Values And Gross Unrealized Losses OTTI Impairment Losses Reported In AOCI [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	20,602,000	21,045,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses	1,514,000	1,845,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	11,736,000	12,273,000
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses	4,132,000	1,268,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	32,338,000	33,318,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses	5,646,000	3,113,000
US States and Political Subdivisions Debt Securities [Member] | External Credit Rating, Non Investment Grade [Member] | Fixed Maturities [Member]
Estimated Fair Values And Gross Unrealized Losses OTTI Impairment Losses Reported In AOCI [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	0	4,000,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses	0	228,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	0	0
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses	0	0
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	0	4,000,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses	0	228,000
Foreign Government Debt Securities [Member] | External Credit Rating, Investment Grade [Member] | Fixed Maturities [Member]
Estimated Fair Values And Gross Unrealized Losses OTTI Impairment Losses Reported In AOCI [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	244,817,000	148,416,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses	1,953,000	1,085,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	7,435,000	16,588,000
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses	761,000	2,491,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	252,252,000	165,004,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses	2,714,000	3,576,000
Commercial Mortgage Backed Securities [Member] | External Credit Rating, Investment Grade [Member] | Fixed Maturities [Member]
Estimated Fair Values And Gross Unrealized Losses OTTI Impairment Losses Reported In AOCI [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	89,507,000	109,455,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses	797,000	3,538,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	29,181,000	58,979,000
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses	7,974,000	22,001,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	118,688,000	168,434,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses	8,771,000	25,539,000
Commercial Mortgage Backed Securities [Member] | External Credit Rating, Non Investment Grade [Member] | Fixed Maturities [Member]
Estimated Fair Values And Gross Unrealized Losses OTTI Impairment Losses Reported In AOCI [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	3,317,000	34,918,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses	764,000	7,220,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	68,405,000	62,357,000
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses	42,307,000	46,730,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	71,722,000	97,275,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses	43,071,000	53,950,000
Residential Mortgage Backed Securities [Member] | External Credit Rating, Investment Grade [Member] | Fixed Maturities [Member]
Estimated Fair Values And Gross Unrealized Losses OTTI Impairment Losses Reported In AOCI [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	22,288,000	128,622,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses	97,000	3,549,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	19,394,000	58,388,000
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses	3,199,000	10,382,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	41,682,000	187,010,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses	3,296,000	13,931,000
Residential Mortgage Backed Securities [Member] | External Credit Rating, Non Investment Grade [Member] | Fixed Maturities [Member]
Estimated Fair Values And Gross Unrealized Losses OTTI Impairment Losses Reported In AOCI [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	15,199,000	23,199,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses	80,000	712,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	2,633,000	10,459,000
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses	347,000	1,781,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	17,832,000	33,658,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses	427,000	2,493,000
Asset-backed Securities [Member] | External Credit Rating, Investment Grade [Member] | Fixed Maturities [Member]
Estimated Fair Values And Gross Unrealized Losses OTTI Impairment Losses Reported In AOCI [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	59,119,000	101,263,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses	449,000	3,592,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	96,179,000	93,910,000
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses	9,508,000	29,036,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	155,298,000	195,173,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses	9,957,000	32,628,000
Asset-backed Securities [Member] | External Credit Rating, Non Investment Grade [Member] | Fixed Maturities [Member]
Estimated Fair Values And Gross Unrealized Losses OTTI Impairment Losses Reported In AOCI [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	3,421,000	2,363,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses	26,000	940,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	31,938,000	21,275,000
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses	18,815,000	20,107,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	35,359,000	23,638,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses	18,841,000	21,047,000
Canadian Provincial Governments [Member] | External Credit Rating, Investment Grade [Member] | Fixed Maturities [Member]
Estimated Fair Values And Gross Unrealized Losses OTTI Impairment Losses Reported In AOCI [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	12,349,000	3,094,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses	174,000	29,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	0	0
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses	0	0
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	12,349,000	3,094,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses	174,000	29,000
Nonredeemable Preferred Stock [Member] | Equity Securities [Member]
Estimated Fair Values And Gross Unrealized Losses OTTI Impairment Losses Reported In AOCI [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	5,577,000	19,516,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses	52,000	4,478,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	5,679,000	15,694,000
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses	118,000	4,504,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	11,256,000	35,210,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses	170,000	8,982,000
Equity Securities, Other [Member] | Equity Securities [Member]
Estimated Fair Values And Gross Unrealized Losses OTTI Impairment Losses Reported In AOCI [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	85,374,000	1,662,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses	1,134,000	602,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	0	5,905,000
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses	0	936,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	85,374,000	7,567,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses	$ 1,134,000	$ 1,538,000