Investments (Details 8) (USD $) In Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2011	Dec. 31, 2010
Corporate Debt Securities Member | External Credit Rating Investment Grade Member | Fixed Maturities Member
Estimated Fair Values And Gross Unrealized Losses Including OTTI Impairment Losses Reported In AOCI [Line Items]
Available For Sale Securities Continuous Unrealized Loss Position Less Than Twelve Months Fair Value	$ 1,051,097	$ 1,170,016
Available For Sale Securities Continuous Unrealized Loss Position Less Than 12 Months Aggregate Losses	22,729	34,097
Available For Sale Securities Continuous Unrealized Loss Position Twelve Months Or Longer Fair Value	322,201	368,128
Available For Sale Securities Continuous Unrealized Loss Position 12 Months Or Longer Aggregate Losses	50,525	61,945
Available For Sale Securities Continuous Unrealized Loss Position Fair Value	1,373,298	1,538,144
Available For Sale Securities Continuous Unrealized Loss Position Aggregate Losses	73,254	96,042
Corporate Debt Securities Member | External Credit Rating Non Investment Grade Member | Fixed Maturities Member
Estimated Fair Values And Gross Unrealized Losses Including OTTI Impairment Losses Reported In AOCI [Line Items]
Available For Sale Securities Continuous Unrealized Loss Position Less Than Twelve Months Fair Value	120,371	58,420
Available For Sale Securities Continuous Unrealized Loss Position Less Than 12 Months Aggregate Losses	2,918	1,832
Available For Sale Securities Continuous Unrealized Loss Position Twelve Months Or Longer Fair Value	65,818	91,205
Available For Sale Securities Continuous Unrealized Loss Position 12 Months Or Longer Aggregate Losses	5,063	9,942
Available For Sale Securities Continuous Unrealized Loss Position Fair Value	186,189	149,625
Available For Sale Securities Continuous Unrealized Loss Position Aggregate Losses	7,981	11,774
US Government Agencies Debt Securities Member | External Credit Rating Investment Grade Member | Fixed Maturities Member
Estimated Fair Values And Gross Unrealized Losses Including OTTI Impairment Losses Reported In AOCI [Line Items]
Available For Sale Securities Continuous Unrealized Loss Position Less Than Twelve Months Fair Value	14,288	11,839
Available For Sale Securities Continuous Unrealized Loss Position Less Than 12 Months Aggregate Losses	602	708
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	14,288	11,839
Available For Sale Securities Continuous Unrealized Loss Position Aggregate Losses	602	708
US States And Political Subdivisions Member | External Credit Rating Investment Grade Member | Fixed Maturities Member
Estimated Fair Values And Gross Unrealized Losses Including OTTI Impairment Losses Reported In AOCI [Line Items]
Available For Sale Securities Continuous Unrealized Loss Position Less Than Twelve Months Fair Value	19,834	68,229
Available For Sale Securities Continuous Unrealized Loss Position Less Than 12 Months Aggregate Losses	985	2,890
Available For Sale Securities Continuous Unrealized Loss Position Twelve Months Or Longer Fair Value	32,473	31,426
Available For Sale Securities Continuous Unrealized Loss Position 12 Months Or Longer Aggregate Losses	4,076	5,227
Available For Sale Securities Continuous Unrealized Loss Position Fair Value	52,307	99,655
Available For Sale Securities Continuous Unrealized Loss Position Aggregate Losses	5,061	8,117
US States And Political Subdivisions Member | External Credit Rating Non Investment Grade Member | Fixed Maturities Member
Estimated Fair Values And Gross Unrealized Losses Including OTTI Impairment Losses Reported In AOCI [Line Items]
Available For Sale Securities Continuous Unrealized Loss Position Less Than Twelve Months Fair Value	0
Available For Sale Securities Continuous Unrealized Loss Position Less Than 12 Months Aggregate Losses	0
Available For Sale Securities Continuous Unrealized Loss Position Twelve Months Or Longer Fair Value	0
Available For Sale Securities Continuous Unrealized Loss Position 12 Months Or Longer Aggregate Losses	0
Available For Sale Securities Continuous Unrealized Loss Position Fair Value	0
Available For Sale Securities Continuous Unrealized Loss Position Aggregate Losses	0
Foreign Government Debt Securities Member | External Credit Rating Investment Grade Member | Fixed Maturities Member
Estimated Fair Values And Gross Unrealized Losses Including OTTI Impairment Losses Reported In AOCI [Line Items]
Available For Sale Securities Continuous Unrealized Loss Position Less Than Twelve Months Fair Value	161,417	322,363
Available For Sale Securities Continuous Unrealized Loss Position Less Than 12 Months Aggregate Losses	3,945	3,142
Available For Sale Securities Continuous Unrealized Loss Position Twelve Months Or Longer Fair Value	39,267	43,796
Available For Sale Securities Continuous Unrealized Loss Position 12 Months Or Longer Aggregate Losses	3,778	4,504
Available For Sale Securities Continuous Unrealized Loss Position Fair Value	200,684	366,159
Available For Sale Securities Continuous Unrealized Loss Position Aggregate Losses	7,723	7,646
Foreign Government Debt Securities Member | External Credit Rating Non Investment Grade Member | Fixed Maturities Member
Estimated Fair Values And Gross Unrealized Losses Including OTTI Impairment Losses Reported In AOCI [Line Items]
Available For Sale Securities Continuous Unrealized Loss Position Less Than Twelve Months Fair Value	0
Available For Sale Securities Continuous Unrealized Loss Position Less Than 12 Months Aggregate Losses	0
Available For Sale Securities Continuous Unrealized Loss Position Twelve Months Or Longer Fair Value	0
Available For Sale Securities Continuous Unrealized Loss Position 12 Months Or Longer Aggregate Losses	0
Available For Sale Securities Continuous Unrealized Loss Position Fair Value	0
Available For Sale Securities Continuous Unrealized Loss Position Aggregate Losses	0
Commercial Mortgage Backed Securities Member | External Credit Rating Investment Grade Member | Fixed Maturities Member
Estimated Fair Values And Gross Unrealized Losses Including OTTI Impairment Losses Reported In AOCI [Line Items]
Available For Sale Securities Continuous Unrealized Loss Position Less Than Twelve Months Fair Value	154,382	132,526
Available For Sale Securities Continuous Unrealized Loss Position Less Than 12 Months Aggregate Losses	8,007	4,143
Available For Sale Securities Continuous Unrealized Loss Position Twelve Months Or Longer Fair Value	68,039	109,158
Available For Sale Securities Continuous Unrealized Loss Position 12 Months Or Longer Aggregate Losses	21,881	29,059
Available For Sale Securities Continuous Unrealized Loss Position Fair Value	222,421	241,684
Available For Sale Securities Continuous Unrealized Loss Position Aggregate Losses	29,888	33,202
Commercial Mortgage Backed Securities Member | External Credit Rating Non Investment Grade Member | Fixed Maturities Member
Estimated Fair Values And Gross Unrealized Losses Including OTTI Impairment Losses Reported In AOCI [Line Items]
Available For Sale Securities Continuous Unrealized Loss Position Less Than Twelve Months Fair Value	22,876	0
Available For Sale Securities Continuous Unrealized Loss Position Less Than 12 Months Aggregate Losses	1,492	0
Available For Sale Securities Continuous Unrealized Loss Position Twelve Months Or Longer Fair Value	80,145	89,170
Available For Sale Securities Continuous Unrealized Loss Position 12 Months Or Longer Aggregate Losses	35,727	64,063
Available For Sale Securities Continuous Unrealized Loss Position Fair Value	103,021	89,170
Available For Sale Securities Continuous Unrealized Loss Position Aggregate Losses	37,219	64,063
Residential Mortgage Backed Securities Member | External Credit Rating Investment Grade Member | Fixed Maturities Member
Estimated Fair Values And Gross Unrealized Losses Including OTTI Impairment Losses Reported In AOCI [Line Items]
Available For Sale Securities Continuous Unrealized Loss Position Less Than Twelve Months Fair Value	122,968	195,406
Available For Sale Securities Continuous Unrealized Loss Position Less Than 12 Months Aggregate Losses	1,979	4,986
Available For Sale Securities Continuous Unrealized Loss Position Twelve Months Or Longer Fair Value	56,186	105,601
Available For Sale Securities Continuous Unrealized Loss Position 12 Months Or Longer Aggregate Losses	10,083	13,607
Available For Sale Securities Continuous Unrealized Loss Position Fair Value	179,154	301,007
Available For Sale Securities Continuous Unrealized Loss Position Aggregate Losses	12,062	18,593
Residential Mortgage Backed Securities Member | External Credit Rating Non Investment Grade Member | Fixed Maturities Member
Estimated Fair Values And Gross Unrealized Losses Including OTTI Impairment Losses Reported In AOCI [Line Items]
Available For Sale Securities Continuous Unrealized Loss Position Less Than Twelve Months Fair Value	5,075	1,162
Available For Sale Securities Continuous Unrealized Loss Position Less Than 12 Months Aggregate Losses	931	605
Available For Sale Securities Continuous Unrealized Loss Position Twelve Months Or Longer Fair Value	11,169	38,206
Available For Sale Securities Continuous Unrealized Loss Position 12 Months Or Longer Aggregate Losses	1,326	7,382
Available For Sale Securities Continuous Unrealized Loss Position Fair Value	16,244	39,368
Available For Sale Securities Continuous Unrealized Loss Position Aggregate Losses	2,257	7,987
Asset Backed Securities Member | External Credit Rating Investment Grade Member | Fixed Maturities Member
Estimated Fair Values And Gross Unrealized Losses Including OTTI Impairment Losses Reported In AOCI [Line Items]
Available For Sale Securities Continuous Unrealized Loss Position Less Than Twelve Months Fair Value	40,152	23,065
Available For Sale Securities Continuous Unrealized Loss Position Less Than 12 Months Aggregate Losses	874	570
Available For Sale Securities Continuous Unrealized Loss Position Twelve Months Or Longer Fair Value	100,050	131,172
Available For Sale Securities Continuous Unrealized Loss Position 12 Months Or Longer Aggregate Losses	29,877	38,451
Available For Sale Securities Continuous Unrealized Loss Position Fair Value	140,202	154,237
Available For Sale Securities Continuous Unrealized Loss Position Aggregate Losses	30,751	39,021
Asset Backed Securities Member | External Credit Rating Non Investment Grade Member | Fixed Maturities Member
Estimated Fair Values And Gross Unrealized Losses Including OTTI Impairment Losses Reported In AOCI [Line Items]
Available For Sale Securities Continuous Unrealized Loss Position Less Than Twelve Months Fair Value	2,852	0
Available For Sale Securities Continuous Unrealized Loss Position Less Than 12 Months Aggregate Losses	424	0
Available For Sale Securities Continuous Unrealized Loss Position Twelve Months Or Longer Fair Value	26,391	23,356
Available For Sale Securities Continuous Unrealized Loss Position 12 Months Or Longer Aggregate Losses	20,467	22,523
Available For Sale Securities Continuous Unrealized Loss Position Fair Value	29,243	23,356
Available For Sale Securities Continuous Unrealized Loss Position Aggregate Losses	20,891	22,523
Canadian Provincial Governments Member | External Credit Rating Investment Grade Member | Fixed Maturities Member
Estimated Fair Values And Gross Unrealized Losses Including OTTI Impairment Losses Reported In AOCI [Line Items]
Available For Sale Securities Continuous Unrealized Loss Position Less Than Twelve Months Fair Value	132,591	118,585
Available For Sale Securities Continuous Unrealized Loss Position Less Than 12 Months Aggregate Losses	2,840	3,886
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	132,591	118,585
Available For Sale Securities Continuous Unrealized Loss Position Aggregate Losses	2,840	3,886
Nonredeemable Preferred Stock Member | Equity Securities Member
Estimated Fair Values And Gross Unrealized Losses Including OTTI Impairment Losses Reported In AOCI [Line Items]
Available For Sale Securities Continuous Unrealized Loss Position Less Than Twelve Months Fair Value	2,291	15,987
Available For Sale Securities Continuous Unrealized Loss Position Less Than 12 Months Aggregate Losses	4	834
Available For Sale Securities Continuous Unrealized Loss Position Twelve Months Or Longer Fair Value	21,100	28,549
Available For Sale Securities Continuous Unrealized Loss Position 12 Months Or Longer Aggregate Losses	2,259	4,464
Available For Sale Securities Continuous Unrealized Loss Position Fair Value	23,391	44,536
Available For Sale Securities Continuous Unrealized Loss Position Aggregate Losses	2,263	5,298
Equity Securities Other Member | Equity Securities Member
Estimated Fair Values And Gross Unrealized Losses Including OTTI Impairment Losses Reported In AOCI [Line Items]
Available For Sale Securities Continuous Unrealized Loss Position Less Than Twelve Months Fair Value	3,551	6,877
Available For Sale Securities Continuous Unrealized Loss Position Less Than 12 Months Aggregate Losses	391	271
Available For Sale Securities Continuous Unrealized Loss Position Twelve Months Or Longer Fair Value	5,887	318
Available For Sale Securities Continuous Unrealized Loss Position 12 Months Or Longer Aggregate Losses	636	0
Available For Sale Securities Continuous Unrealized Loss Position Fair Value	9,438	7,195
Available For Sale Securities Continuous Unrealized Loss Position Aggregate Losses	1,027	271
Available For Sale Securities In Unrealized Loss Positions Qualitative Disclosure Number Of Positions Member
Estimated Fair Values And Gross Unrealized Losses Including OTTI Impairment Losses Reported In AOCI [Line Items]
Available For Sale Securities Continuous Unrealized Loss Position Less Than Twelve Months Fair Value	550	520
Available For Sale Securities Continuous Unrealized Loss Position Twelve Months Or Longer Fair Value	411	508
Available For Sale Securities Continuous Unrealized Loss Position Fair Value	961	1,028
External Credit Rating Investment Grade Member | Fixed Maturities Member
Estimated Fair Values And Gross Unrealized Losses Including OTTI Impairment Losses Reported In AOCI [Line Items]
Available For Sale Securities Continuous Unrealized Loss Position Less Than Twelve Months Fair Value	1,696,729	2,042,029
Available For Sale Securities Continuous Unrealized Loss Position Less Than 12 Months Aggregate Losses	41,961	54,422
Available For Sale Securities Continuous Unrealized Loss Position Twelve Months Or Longer Fair Value	618,216	789,281
Available For Sale Securities Continuous Unrealized Loss Position 12 Months Or Longer Aggregate Losses	120,220	152,793
Available For Sale Securities Continuous Unrealized Loss Position Fair Value	2,314,945	2,831,310
Available For Sale Securities Continuous Unrealized Loss Position Aggregate Losses	162,181	207,215
External Credit Rating Non Investment Grade Member | Fixed Maturities Member
Estimated Fair Values And Gross Unrealized Losses Including OTTI Impairment Losses Reported In AOCI [Line Items]
Available For Sale Securities Continuous Unrealized Loss Position Less Than Twelve Months Fair Value	151,174	59,582
Available For Sale Securities Continuous Unrealized Loss Position Less Than 12 Months Aggregate Losses	5,765	2,437
Available For Sale Securities Continuous Unrealized Loss Position Twelve Months Or Longer Fair Value	183,523	241,937
Available For Sale Securities Continuous Unrealized Loss Position 12 Months Or Longer Aggregate Losses	62,583	103,910
Available For Sale Securities Continuous Unrealized Loss Position Fair Value	334,697	301,519
Available For Sale Securities Continuous Unrealized Loss Position Aggregate Losses	68,348	106,347
Fixed Maturities Member
Estimated Fair Values And Gross Unrealized Losses Including OTTI Impairment Losses Reported In AOCI [Line Items]
Available For Sale Securities Continuous Unrealized Loss Position Less Than Twelve Months Fair Value	1,847,903	2,101,611
Available For Sale Securities Continuous Unrealized Loss Position Less Than 12 Months Aggregate Losses	47,726	56,859
Available For Sale Securities Continuous Unrealized Loss Position Twelve Months Or Longer Fair Value	801,739	1,031,218
Available For Sale Securities Continuous Unrealized Loss Position 12 Months Or Longer Aggregate Losses	182,803	256,703
Available For Sale Securities Continuous Unrealized Loss Position Fair Value	2,649,642	3,132,829
Available For Sale Securities Continuous Unrealized Loss Position Aggregate Losses	230,529	313,562
Equity Securities Member
Estimated Fair Values And Gross Unrealized Losses Including OTTI Impairment Losses Reported In AOCI [Line Items]
Available For Sale Securities Continuous Unrealized Loss Position Less Than Twelve Months Fair Value	5,842	22,864
Available For Sale Securities Continuous Unrealized Loss Position Less Than 12 Months Aggregate Losses	395	1,105
Available For Sale Securities Continuous Unrealized Loss Position Twelve Months Or Longer Fair Value	26,987	28,867
Available For Sale Securities Continuous Unrealized Loss Position 12 Months Or Longer Aggregate Losses	2,895	4,464
Available For Sale Securities Continuous Unrealized Loss Position Fair Value	32,829	51,731
Available For Sale Securities Continuous Unrealized Loss Position Aggregate Losses	$ 3,290	$ 5,569