Investments - Narrative (Details) (USD $)	12 Months Ended			0 Months Ended
	Dec. 31, 2014 positions	Dec. 31, 2013	Dec. 31, 2012	May 01, 2014
Schedule Of Available For Sale And Held To Maturity Securities [Line Items]
Fixed maturities, held to maturity, gross unrealized losses	$ 0
Cumulative adjustments recorded to value of future policy benefit reserves, amount	400,456,000	44,660,000	0
Fixed maturities, AFS, at fair value	29,359,034,000	27,500,136,000
Amortized cost of fixed maturities, available for sale	27,728,771,000	27,111,874,000
Fixed maturities, held to maturity	0	2,858,695,000
Fair value of held to maturity securities	0	3,131,235,000
Percentage of fixed income portfolio invested in securities below investment grade	3.00%	2.60%
Percentage of gross unrealized losses relating to securities below investment grade	24.90%	12.40%
Pledged assets, amount	15,200,000,000	15,500,000,000
Available For Sale Securities Gross Unrealized Loss Accumulated In Investments	213,576,000	437,036,000
Total number of positions - AFS	7,669
AFS securities in unrealized loss position (number of positions)	1,631
OTTI on investments, net of amounts transferred to other comprehensive income	35,700,000
Credit loss impairments previously recognized on securities which matured, paid down, prepaid or were sold during the period	42,671,000	92,167,000
Equity securities, AFS, at fair value	868,292,000	1,040,237,000
Cost of equity securities, available for sale	763,833,000	903,201,000
Corporate
Schedule Of Available For Sale And Held To Maturity Securities [Line Items]
Fixed maturities, held to maturity, gross unrealized gains		113,179,000
Fixed maturities, held to maturity, gross unrealized losses		(968,000)
Fixed maturities, AFS, at fair value		11,125,830,000
Amortized cost of fixed maturities, available for sale		10,802,332,000
Fixed maturities, held to maturity		1,386,863,000
Fair value of held to maturity securities		1,499,074,000
OTTI on investments, net of amounts transferred to other comprehensive income	3,700,000
Medium-term Notes [Member]
Schedule Of Available For Sale And Held To Maturity Securities [Line Items]
Fixed maturities, AFS, at fair value	79,900,000	154,600,000
Amortized cost of fixed maturities, available for sale	68,400,000	147,700,000
Fixed Income Funds Member
Schedule Of Available For Sale And Held To Maturity Securities [Line Items]
Cost of equity securities, available for sale	100,000,000
Structured Credit Securities [Member]
Schedule Of Available For Sale And Held To Maturity Securities [Line Items]
Fair value	5,500,000
Marketable Securities Unrealized Loss Other Than Temporary Impairments Amount	9,600,000
Impaired Investment Cumulative Fair Value Decline Percentage Amortized Cost	50.00%
Other Investments [Member]
Schedule Of Available For Sale And Held To Maturity Securities [Line Items]
OTTI on investments, net of amounts transferred to other comprehensive income	12,500,000
RMBS - Non-Agency
Schedule Of Available For Sale And Held To Maturity Securities [Line Items]
Fixed maturities, held to maturity, gross unrealized gains		4,985,000
Fixed maturities, held to maturity, gross unrealized losses		0
Fixed maturities, AFS, at fair value		398,768,000
Amortized cost of fixed maturities, available for sale		396,798,000
Fixed maturities, held to maturity		66,987,000
Fair value of held to maturity securities		71,972,000
OTTI on investments, net of amounts transferred to other comprehensive income	4,300,000
Credit loss impairments previously recognized on securities which matured, paid down, prepaid or were sold during the period	9,000,000	66,100,000
Currency losses
Schedule Of Available For Sale And Held To Maturity Securities [Line Items]
OTTI on investments, net of amounts transferred to other comprehensive income	4,200,000
CMBS
Schedule Of Available For Sale And Held To Maturity Securities [Line Items]
Fixed maturities, held to maturity, gross unrealized gains		11,864,000
Fixed maturities, held to maturity, gross unrealized losses		0
Fixed maturities, AFS, at fair value		1,246,795,000
Amortized cost of fixed maturities, available for sale		1,223,313,000
Fixed maturities, held to maturity		144,924,000
Fair value of held to maturity securities		156,788,000
XL Re Life (SAC) Ltd [Member]
Schedule Of Available For Sale And Held To Maturity Securities [Line Items]
Held To Maturity Securities Transferred Security Carrying Value				2,800,000,000
Fixed maturities, held to maturity, gross unrealized gains				424,900,000
Fixed maturities, held to maturity, gross unrealized losses				0
Unrealized Gains (Losses) on Investments
Schedule Of Available For Sale And Held To Maturity Securities [Line Items]
Cumulative adjustments recorded to value of future policy benefit reserves, amount	400,456,000
Unrealized Gains (Losses) on Investments | XL Re Life (SAC) Ltd [Member]
Schedule Of Available For Sale And Held To Maturity Securities [Line Items]
Cumulative adjustments recorded to value of future policy benefit reserves, amount				440,500,000
Exclude Life Funds Withheld Assets [Member]
Schedule Of Available For Sale And Held To Maturity Securities [Line Items]
Fixed maturities, AFS, at fair value	24,177,469,000	27,500,136,000
Amortized cost of fixed maturities, available for sale	23,427,432,000	27,111,874,000
Available For Sale Securities Gross Unrealized Loss Accumulated In Investments	213,576,000
Equity securities, AFS, at fair value	868,292,000
Cost of equity securities, available for sale	763,833,000
Exclude Life Funds Withheld Assets [Member] | Corporate
Schedule Of Available For Sale And Held To Maturity Securities [Line Items]
Fixed maturities, AFS, at fair value	8,778,373,000
Amortized cost of fixed maturities, available for sale	8,462,130,000
Exclude Life Funds Withheld Assets [Member] | Equity securities
Schedule Of Available For Sale And Held To Maturity Securities [Line Items]
OTTI on investments, net of amounts transferred to other comprehensive income	10,944,000	17,000	3,746,000
Exclude Life Funds Withheld Assets [Member] | RMBS - Non-Agency
Schedule Of Available For Sale And Held To Maturity Securities [Line Items]
Fixed maturities, AFS, at fair value	427,351,000
Amortized cost of fixed maturities, available for sale	404,398,000
Exclude Life Funds Withheld Assets [Member] | CMBS
Schedule Of Available For Sale And Held To Maturity Securities [Line Items]
Fixed maturities, AFS, at fair value	1,052,544,000
Amortized cost of fixed maturities, available for sale	$ 1,033,819,000