Investments - Cost (amortized cost for fixed maturities and short-term investments), fair value, gross unrealized gains, gross unrealized (losses), and OTTI recorded in AOCI (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2014		May 01, 2014	Dec. 31, 2013
AFS securities
Cost or amortized cost of Fixed maturities	$ 29,065,531			$ 27,111,874
Gross unrealized gains on Fixed maturities				807,684
Gross unrealized losses on Fixed maturities				(419,422)
Fixed maturities, at fair value	30,442,921			27,500,136
Gross Unrealized Losses Non-credit related OTTI	(81,834)			(86,882)	[1]
Short-term investments, amortized cost	347,473			455,470
Short-term investments, gross unrealized gains	972	[2]		962	[3]
Short-term investments, gross unrealized losses	(771)	[2]		(144)	[3]
Short-term investments, at fair value	347,674			456,288
Cost of equity securities	839,716			903,201
Equity securities, gross unrealized gains	151,618	[4]		154,506	[5]
Equity securities, gross unrealized losses	(2,624)	[4]		(17,470)	[5]
Equity securities, at fair value	988,710			1,040,237
Available for sale securities, Cost or amortized cost	30,252,720			28,470,545
Available for sale securities, Gross unrealized gains	1,695,830			963,152
Available for sale securities, Gross unrealized losses	(169,245)			(437,036)
Total investments available for sale	31,779,305			28,996,661
Fixed maturities - HTM
Fixed maturities, held to maturity	0			2,858,695
Fixed maturites held to maturity, gross unrealized gains	0		424,861	274,150
Fixed maturites held to maturity, gross unrealized losses	0		0	(1,610)
Fair value of held to maturity securities	0			3,131,235
U.S. Government and Government - Related/Supported
AFS securities
Cost or amortized cost of Fixed maturities				2,484,193
Gross unrealized gains on Fixed maturities				51,701	[3]
Gross unrealized losses on Fixed maturities				(34,043)	[3]
Fixed maturities, at fair value				2,501,851
Gross Unrealized Losses Non-credit related OTTI				0	[1],[3]
Fixed maturities - HTM
Fixed maturities, held to maturity	0			10,993
Fixed maturites held to maturity, gross unrealized gains				629	[3]
Fixed maturites held to maturity, gross unrealized losses				0	[3]
Fair value of held to maturity securities				11,622
Corporate
AFS securities
Cost or amortized cost of Fixed maturities				10,802,332
Gross unrealized gains on Fixed maturities				433,097	[6],[7]
Gross unrealized losses on Fixed maturities				(109,599)	[6],[7]
Fixed maturities, at fair value				11,125,830
Gross Unrealized Losses Non-credit related OTTI				(4,758)	[1],[6],[7]
Fixed maturities - HTM
Fixed maturities, held to maturity				1,386,863
Fixed maturites held to maturity, gross unrealized gains				113,179
Fixed maturites held to maturity, gross unrealized losses				(968)
Fair value of held to maturity securities				1,499,074
RMBS - Agency
AFS securities
Cost or amortized cost of Fixed maturities				3,540,101
Gross unrealized gains on Fixed maturities				68,098
Gross unrealized losses on Fixed maturities				(62,077)
Fixed maturities, at fair value				3,546,122
Gross Unrealized Losses Non-credit related OTTI				0	[1]
RMBS - Non-Agency
AFS securities
Cost or amortized cost of Fixed maturities				396,798
Gross unrealized gains on Fixed maturities				33,096
Gross unrealized losses on Fixed maturities				(31,126)
Fixed maturities, at fair value				398,768
Gross Unrealized Losses Non-credit related OTTI				(74,528)	[1]
Fixed maturities - HTM
Fixed maturities, held to maturity	0			66,987
Fixed maturites held to maturity, gross unrealized gains				4,985
Fixed maturites held to maturity, gross unrealized losses				0
Fair value of held to maturity securities				71,972
CMBS
AFS securities
Cost or amortized cost of Fixed maturities				1,223,313
Gross unrealized gains on Fixed maturities				39,255
Gross unrealized losses on Fixed maturities				(15,773)
Fixed maturities, at fair value				1,246,795
Gross Unrealized Losses Non-credit related OTTI				(2,753)	[1]
Fixed maturities - HTM
Fixed maturities, held to maturity	0			144,924
Fixed maturites held to maturity, gross unrealized gains				11,864
Fixed maturites held to maturity, gross unrealized losses				0
Fair value of held to maturity securities				156,788
CDO
AFS securities
Cost or amortized cost of Fixed maturities				754,414
Gross unrealized gains on Fixed maturities				5,833
Gross unrealized losses on Fixed maturities				(42,934)
Fixed maturities, at fair value				717,313
Gross Unrealized Losses Non-credit related OTTI				(2,036)	[1]
Other asset-backed securities
AFS securities
Cost or amortized cost of Fixed maturities				1,210,384
Gross unrealized gains on Fixed maturities				40,560	[8]
Gross unrealized losses on Fixed maturities				(8,840)	[8]
Fixed maturities, at fair value				1,242,104
Gross Unrealized Losses Non-credit related OTTI				(2,807)	[1],[8]
Fixed maturities - HTM
Fixed maturities, held to maturity	0			106,540
Fixed maturites held to maturity, gross unrealized gains				6,908	[8]
Fixed maturites held to maturity, gross unrealized losses				0	[8]
Fair value of held to maturity securities				113,448
U.S. States and political subdivisions of the States
AFS securities
Cost or amortized cost of Fixed maturities				1,821,499
Gross unrealized gains on Fixed maturities				55,083
Gross unrealized losses on Fixed maturities				(30,770)
Fixed maturities, at fair value				1,845,812
Gross Unrealized Losses Non-credit related OTTI				0	[1]
Non-U.S. Sovereign Government, Provincial, Supranational, and Government-Related/Supported
AFS securities
Cost or amortized cost of Fixed maturities				4,878,840
Gross unrealized gains on Fixed maturities				80,961	[3]
Gross unrealized losses on Fixed maturities				(84,260)	[3]
Fixed maturities, at fair value				4,875,541
Gross Unrealized Losses Non-credit related OTTI				0	[1],[3]
Fixed maturities - HTM
Fixed maturities, held to maturity	0			1,142,388
Fixed maturites held to maturity, gross unrealized gains				136,585	[3]
Fixed maturites held to maturity, gross unrealized losses				(642)	[3]
Fair value of held to maturity securities				1,278,331
Excluding Life Funds Withheld Assets
AFS securities
Cost or amortized cost of Fixed maturities	24,226,460
Gross unrealized gains on Fixed maturities	937,940
Gross unrealized losses on Fixed maturities	(165,850)
Fixed maturities, at fair value	24,998,550
Gross Unrealized Losses Non-credit related OTTI	(81,834)	[1]
Available for sale securities, Cost or amortized cost	25,413,649
Available for sale securities, Gross unrealized gains	1,090,530
Available for sale securities, Gross unrealized losses	(169,245)
Total investments available for sale	26,334,934
Excluding Life Funds Withheld Assets | U.S. Government and Government - Related/Supported
AFS securities
Cost or amortized cost of Fixed maturities	2,033,152
Gross unrealized gains on Fixed maturities	60,408	[2]
Gross unrealized losses on Fixed maturities	(9,266)	[2]
Fixed maturities, at fair value	2,084,294
Gross Unrealized Losses Non-credit related OTTI	0	[1],[2]
Excluding Life Funds Withheld Assets | Corporate
AFS securities
Cost or amortized cost of Fixed maturities	9,345,654
Gross unrealized gains on Fixed maturities	425,093	[10],[9]
Gross unrealized losses on Fixed maturities	(43,123)	[10],[9]
Fixed maturities, at fair value	9,727,624
Gross Unrealized Losses Non-credit related OTTI	(4,758)	[1],[10],[9]
Excluding Life Funds Withheld Assets | RMBS - Agency
AFS securities
Cost or amortized cost of Fixed maturities	3,218,551
Gross unrealized gains on Fixed maturities	104,874
Gross unrealized losses on Fixed maturities	(20,379)
Fixed maturities, at fair value	3,303,046
Gross Unrealized Losses Non-credit related OTTI	0	[1]
Excluding Life Funds Withheld Assets | RMBS - Non-Agency
AFS securities
Cost or amortized cost of Fixed maturities	395,629
Gross unrealized gains on Fixed maturities	41,054
Gross unrealized losses on Fixed maturities	(21,180)
Fixed maturities, at fair value	415,503
Gross Unrealized Losses Non-credit related OTTI	(70,645)	[1]
Excluding Life Funds Withheld Assets | CMBS
AFS securities
Cost or amortized cost of Fixed maturities	1,098,149
Gross unrealized gains on Fixed maturities	33,562
Gross unrealized losses on Fixed maturities	(7,424)
Fixed maturities, at fair value	1,124,287
Gross Unrealized Losses Non-credit related OTTI	(2,561)	[1]
Excluding Life Funds Withheld Assets | CDO
AFS securities
Cost or amortized cost of Fixed maturities	763,146
Gross unrealized gains on Fixed maturities	3,656
Gross unrealized losses on Fixed maturities	(28,729)
Fixed maturities, at fair value	738,073
Gross Unrealized Losses Non-credit related OTTI	(1,812)	[1]
Excluding Life Funds Withheld Assets | Other asset-backed securities
AFS securities
Cost or amortized cost of Fixed maturities	1,271,201
Gross unrealized gains on Fixed maturities	42,158	[11]
Gross unrealized losses on Fixed maturities	(3,087)	[11]
Fixed maturities, at fair value	1,310,272
Gross Unrealized Losses Non-credit related OTTI	(2,058)	[1],[11]
Excluding Life Funds Withheld Assets | U.S. States and political subdivisions of the States
AFS securities
Cost or amortized cost of Fixed maturities	1,836,889
Gross unrealized gains on Fixed maturities	109,258
Gross unrealized losses on Fixed maturities	(6,557)
Fixed maturities, at fair value	1,939,590
Gross Unrealized Losses Non-credit related OTTI	0	[1]
Excluding Life Funds Withheld Assets | Non-U.S. Sovereign Government, Provincial, Supranational, and Government-Related/Supported
AFS securities
Cost or amortized cost of Fixed maturities	4,264,089
Gross unrealized gains on Fixed maturities	117,877	[2]
Gross unrealized losses on Fixed maturities	(26,105)	[2]
Fixed maturities, at fair value	4,355,861
Gross Unrealized Losses Non-credit related OTTI	0	[1],[2]
Life Funds Withheld Assets
AFS securities
Cost or amortized cost of Fixed maturities	4,839,071
Gross unrealized gains on Fixed maturities	605,300
Gross unrealized losses on Fixed maturities	0
Fixed maturities, at fair value	5,444,371			0
Gross Unrealized Losses Non-credit related OTTI	0
Life Funds Withheld Assets | U.S. Government and Government - Related/Supported
AFS securities
Cost or amortized cost of Fixed maturities	16,356
Gross unrealized gains on Fixed maturities	1,869
Gross unrealized losses on Fixed maturities	0
Fixed maturities, at fair value	18,225
Gross Unrealized Losses Non-credit related OTTI	0
Life Funds Withheld Assets | Corporate
AFS securities
Cost or amortized cost of Fixed maturities	2,722,907
Gross unrealized gains on Fixed maturities	294,539
Gross unrealized losses on Fixed maturities	0
Fixed maturities, at fair value	3,017,446
Gross Unrealized Losses Non-credit related OTTI	0
Life Funds Withheld Assets | RMBS - Agency
AFS securities
Cost or amortized cost of Fixed maturities	3,990
Gross unrealized gains on Fixed maturities	33
Gross unrealized losses on Fixed maturities	0
Fixed maturities, at fair value	4,023
Gross Unrealized Losses Non-credit related OTTI	0
Life Funds Withheld Assets | RMBS - Non-Agency
AFS securities
Cost or amortized cost of Fixed maturities	78,804
Gross unrealized gains on Fixed maturities	9,300
Gross unrealized losses on Fixed maturities	0
Fixed maturities, at fair value	88,104
Gross Unrealized Losses Non-credit related OTTI	0
Life Funds Withheld Assets | CMBS
AFS securities
Cost or amortized cost of Fixed maturities	198,576
Gross unrealized gains on Fixed maturities	18,268
Gross unrealized losses on Fixed maturities	0
Fixed maturities, at fair value	216,844
Gross Unrealized Losses Non-credit related OTTI	0
Life Funds Withheld Assets | CDO
AFS securities
Cost or amortized cost of Fixed maturities	0
Gross unrealized gains on Fixed maturities	0
Gross unrealized losses on Fixed maturities	0
Fixed maturities, at fair value	0
Gross Unrealized Losses Non-credit related OTTI	0
Life Funds Withheld Assets | Other asset-backed securities
AFS securities
Cost or amortized cost of Fixed maturities	271,691
Gross unrealized gains on Fixed maturities	21,926
Gross unrealized losses on Fixed maturities	0
Fixed maturities, at fair value	293,617
Gross Unrealized Losses Non-credit related OTTI	0
Life Funds Withheld Assets | U.S. States and political subdivisions of the States
AFS securities
Cost or amortized cost of Fixed maturities	0
Gross unrealized gains on Fixed maturities	0
Gross unrealized losses on Fixed maturities	0
Fixed maturities, at fair value	0
Gross Unrealized Losses Non-credit related OTTI	0
Life Funds Withheld Assets | Non-U.S. Sovereign Government, Provincial, Supranational, and Government-Related/Supported
AFS securities
Cost or amortized cost of Fixed maturities	1,546,747
Gross unrealized gains on Fixed maturities	259,365
Gross unrealized losses on Fixed maturities	0
Fixed maturities, at fair value	1,806,112
Gross Unrealized Losses Non-credit related OTTI	$ 0

[1] Represents the non-credit component of OTTI losses, adjusted for subsequent sales of securities. It does not include the change in fair value subsequent to the date an impairment was recorded.

[2] U.S. Government and Government-Related/Supported, Non-U.S. Sovereign Government, Provincials, Supranationals and Government-Related/Supported and Total short-term investments includes government-related securities with an amortized cost of $1,679.1 million and fair value of $1,721.8 million and U.S. Agencies with an amortized cost of $230.2 million and fair value of $256.8 million.

[3] U.S. Government and Government-Related/Supported, Non-U.S. Sovereign Government, Provincials, Supranationals and Government-Related/Supported and Total short-term investments includes government-related securities with an amortized cost of $2,241.5 million and fair value of $2,275.6 million and U.S. Agencies with an amortized cost of $267.0 million and fair value of $284.3 million.

[4] Included within Total equity securities are investments in fixed income funds with a fair value of $92.1 million and an amortized cost of $92.1 million.

[5] Included within Total equity securities are investments in fixed income funds with a fair value of $87.4 million and an amortized cost of $100.0 million.

[6] Included within Corporate are certain medium term notes supported primarily by pools of European investment grade credit with varying degrees of leverage. The notes have a fair value of $154.6 million and an amortized cost of $147.7 million. These notes allow the investor to participate in cash flows of the underlying bonds including certain residual values, which could serve to either decrease or increase the ultimate values of these notes.

[7] Included within Corporate are Tier One and Upper Tier Two securities, representing committed term debt and hybrid instruments, which are senior to the common and preferred equities of the financial institutions. These securities have a fair value of $282.2 million and an amortized cost of $286.2 million.

[8] Covered Bonds within Fixed maturities - AFS with an amortized cost of $526.4 million and a fair value of $553.1 million and Covered Bonds within Fixed maturities - HTM with an amortized cost of $8.6 million and a fair value of $8.7 million are included within Other asset-backed securities to align the Company's classification to market indices.

[9] Included within Corporate are Tier One and Upper Tier Two securities, representing committed term debt and hybrid instruments, which are senior to the common and preferred equities of the financial institutions. These securities have a fair value of $28.1 million and an amortized cost of $32.6 million.

[10] Included within Corporate are certain medium term notes supported primarily by pools of European investment grade credit with varying degrees of leverage. The notes have a fair value of $155.9 million and an amortized cost of $143.6 million. These notes allow the investor to participate in cash flows of the underlying bonds including certain residual values, which could serve to either decrease or increase the ultimate values of these notes.

[11] Covered Bonds with an amortized cost of $737.0 million and a fair value of $763.6 million are included within Other asset-backed securities to align the Company's classification to market indices.