Investments - Contractual maturities of available for sale securities and held to maturity income securities (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Fixed Maturities - AFS
Due less than one year, amortized cost		$ 2,052,251
Due less than one year, fair value		2,060,365
Due after 1 through 5 years, amortized cost		10,075,087
Due after 1 through 5 years, fair value		10,305,986
Due after 5 through 10 years, amortized cost		5,474,120
Due after 5 through 10 years, fair value		5,507,450
Due after 10 years, amortized cost		2,385,406
Due after 10 years, fair value		2,475,233
Subtotal - amortized cost		19,986,864
Subtotal - fair value		20,349,034
Mortgage and asset backed securities - amortized cost		7,125,010
Mortgage and asset backed securities - fair value		7,151,102
Amortized cost of Fixed maturities	28,418,354	27,111,874
Fixed maturities, at fair value	29,806,144	27,500,136
Fixed maturities - HTM
Due less than one year, amortized cost	0	65,651
Due less than one year, fair value	0	66,766
Due after 1 through 5 years, amortized cost	0	240,802
Due after 1 through 5 years, fair value	0	255,322
Due after 5 through 10 years, amortized cost	0	455,633
Due after 5 through 10 years, fair value	0	492,095
Due after 10 years, amortized cost	0	1,778,158
Due after 10 years, fair value	0	1,974,844
Subtotal - amortized cost	0	2,540,244
Subtotal - fair value	0	2,789,027
Mortgage and asset backed securities - amortized cost	0	318,451
Mortgage and asset backed securities - fair value	0	342,208
Fixed maturities, held to maturity	0	2,858,695
Fair value of held to maturity securities	0	3,131,235
RMBS - Agency
Fixed Maturities - AFS
Mortgage and asset backed securities - amortized cost		3,540,101
Mortgage and asset backed securities - fair value		3,546,122
Fixed maturities, at fair value		3,546,122
RMBS - Non-Agency
Fixed Maturities - AFS
Mortgage and asset backed securities - amortized cost		396,798
Mortgage and asset backed securities - fair value		398,768
Fixed maturities, at fair value		398,768
Fixed maturities - HTM
Mortgage and asset backed securities - amortized cost	0	66,987
Mortgage and asset backed securities - fair value	0	71,972
Fixed maturities, held to maturity	0	66,987
Fair value of held to maturity securities		71,972
CMBS
Fixed Maturities - AFS
Mortgage and asset backed securities - amortized cost		1,223,313
Mortgage and asset backed securities - fair value		1,246,795
Fixed maturities, at fair value		1,246,795
Fixed maturities - HTM
Mortgage and asset backed securities - amortized cost	0	144,924
Mortgage and asset backed securities - fair value	0	156,788
Fixed maturities, held to maturity	0	144,924
Fair value of held to maturity securities		156,788
CDO
Fixed Maturities - AFS
Mortgage and asset backed securities - amortized cost		754,414
Mortgage and asset backed securities - fair value		717,313
Fixed maturities, at fair value		717,313
Other asset-backed securities
Fixed Maturities - AFS
Mortgage and asset backed securities - amortized cost		1,210,384
Mortgage and asset backed securities - fair value		1,242,104
Fixed maturities, at fair value		1,242,104
Fixed maturities - HTM
Mortgage and asset backed securities - amortized cost	0	106,540
Mortgage and asset backed securities - fair value	0	113,448
Fixed maturities, held to maturity	0	106,540
Fair value of held to maturity securities		113,448
Excluding Life Funds Withheld Assets
Fixed Maturities - AFS
Due less than one year, amortized cost	1,981,701
Due less than one year, fair value	1,993,518
Due after 1 through 5 years, amortized cost	9,124,512
Due after 1 through 5 years, fair value	9,338,985
Due after 5 through 10 years, amortized cost	4,615,311
Due after 5 through 10 years, fair value	4,778,486
Due after 10 years, amortized cost	1,496,183
Due after 10 years, fair value	1,658,181
Subtotal - amortized cost	17,217,707
Subtotal - fair value	17,769,170
Mortgage and asset backed securities - amortized cost	6,643,858
Mortgage and asset backed securities - fair value	6,773,889
Amortized cost of Fixed maturities	23,861,565
Fixed maturities, at fair value	24,543,059
Excluding Life Funds Withheld Assets | RMBS - Agency
Fixed Maturities - AFS
Mortgage and asset backed securities - amortized cost	3,263,848
Mortgage and asset backed securities - fair value	3,334,882
Fixed maturities, at fair value	3,334,882
Excluding Life Funds Withheld Assets | RMBS - Non-Agency
Fixed Maturities - AFS
Mortgage and asset backed securities - amortized cost	412,443
Mortgage and asset backed securities - fair value	435,654
Fixed maturities, at fair value	435,654
Excluding Life Funds Withheld Assets | CMBS
Fixed Maturities - AFS
Mortgage and asset backed securities - amortized cost	1,081,102
Mortgage and asset backed securities - fair value	1,099,253
Fixed maturities, at fair value	1,099,253
Excluding Life Funds Withheld Assets | CDO
Fixed Maturities - AFS
Mortgage and asset backed securities - amortized cost	770,139
Mortgage and asset backed securities - fair value	746,635
Fixed maturities, at fair value	746,635
Excluding Life Funds Withheld Assets | Other asset-backed securities
Fixed Maturities - AFS
Mortgage and asset backed securities - amortized cost	1,116,326
Mortgage and asset backed securities - fair value	1,157,465
Fixed maturities, at fair value	1,157,465
Life Funds Withheld Assets
Fixed Maturities - AFS
Due less than one year, amortized cost	130,449	0
Due less than one year, fair value	137,349	0
Due after 1 through 5 years, amortized cost	635,771	0
Due after 1 through 5 years, fair value	678,389	0
Due after 5 through 10 years, amortized cost	1,092,313	0
Due after 5 through 10 years, fair value	1,233,845	0
Due after 10 years, amortized cost	2,187,828	0
Due after 10 years, fair value	2,644,487	0
Subtotal - amortized cost	4,046,361	0
Subtotal - fair value	4,694,070	0
Mortgage and asset backed securities - amortized cost	510,428	0
Mortgage and asset backed securities - fair value	569,015	0
Amortized cost of Fixed maturities	4,556,789	0
Fixed maturities, at fair value	5,263,085	0
Life Funds Withheld Assets | RMBS - Agency
Fixed Maturities - AFS
Mortgage and asset backed securities - amortized cost	3,580	0
Mortgage and asset backed securities - fair value	3,896	0
Fixed maturities, at fair value	3,896
Life Funds Withheld Assets | RMBS - Non-Agency
Fixed Maturities - AFS
Mortgage and asset backed securities - amortized cost	75,092	0
Mortgage and asset backed securities - fair value	86,542	0
Fixed maturities, at fair value	86,542
Life Funds Withheld Assets | CMBS
Fixed Maturities - AFS
Mortgage and asset backed securities - amortized cost	180,432	0
Mortgage and asset backed securities - fair value	200,348	0
Fixed maturities, at fair value	200,348
Life Funds Withheld Assets | CDO
Fixed Maturities - AFS
Mortgage and asset backed securities - amortized cost	0	0
Mortgage and asset backed securities - fair value	0	0
Fixed maturities, at fair value	0
Life Funds Withheld Assets | Other asset-backed securities
Fixed Maturities - AFS
Mortgage and asset backed securities - amortized cost	251,324	0
Mortgage and asset backed securities - fair value	278,229	0
Fixed maturities, at fair value	$ 278,229