Investments (Details 8) (USD $)	Mar. 31, 2012	Dec. 31, 2011
Non-Sovereign Fixed Maturity and Equity Securities in European Peripheral Region [Line Items]
Available For Sale Securities Amortized Cost	$ 7,518,983,000	$ 6,931,958,000
Available For Sale Securities Fair Value Disclosure	8,111,454,000	7,461,106,000
Combined European Peripheral Region [Member]
Non-Sovereign Fixed Maturity and Equity Securities in European Peripheral Region [Line Items]
Available For Sale Securities Amortized Cost	69,720,000	79,480,000
Available For Sale Securities Fair Value Disclosure	69,077,000	73,869,000
Percentage Of Total Available For Sales Securities	100.00%	100.00%
Finance Industry [Member]
Non-Sovereign Fixed Maturity and Equity Securities in European Peripheral Region [Line Items]
Available For Sale Securities Amortized Cost	29,816,000	29,649,000
Available For Sale Securities Fair Value Disclosure	28,284,000	24,775,000
Percentage Of Total Available For Sales Securities	40.90%	33.50%
Finance Industry [Member] \| Ireland [Member]
Non-Sovereign Fixed Maturity and Equity Securities in European Peripheral Region [Line Items]
Available For Sale Securities Amortized Cost	4,160,000	4,084,000
Available For Sale Securities Fair Value Disclosure	4,569,000	4,397,000
Percentage Of Total Available For Sales Securities	6.60%	5.90%
Finance Industry [Member] \| Spain [Member]
Non-Sovereign Fixed Maturity and Equity Securities in European Peripheral Region [Line Items]
Available For Sale Securities Amortized Cost	25,656,000	25,565,000
Available For Sale Securities Fair Value Disclosure	23,715,000	20,378,000
Percentage Of Total Available For Sales Securities	34.30%	27.60%
Other Industry [Member]
Non-Sovereign Fixed Maturity and Equity Securities in European Peripheral Region [Line Items]
Available For Sale Securities Amortized Cost	39,904,000	49,831,000
Available For Sale Securities Fair Value Disclosure	40,793,000	49,094,000
Percentage Of Total Available For Sales Securities	59.10%	66.50%
Other Industry [Member] \| Ireland [Member]
Non-Sovereign Fixed Maturity and Equity Securities in European Peripheral Region [Line Items]
Available For Sale Securities Amortized Cost	12,475,000	12,474,000
Available For Sale Securities Fair Value Disclosure	13,285,000	13,149,000
Percentage Of Total Available For Sales Securities	19.30%	17.80%
Other Industry [Member] \| Italy [Member]
Non-Sovereign Fixed Maturity and Equity Securities in European Peripheral Region [Line Items]
Available For Sale Securities Amortized Cost	2,980,000	2,898,000
Available For Sale Securities Fair Value Disclosure	3,058,000	2,808,000
Percentage Of Total Available For Sales Securities	4.40%	3.80%
Other Industry [Member] \| Spain [Member]
Non-Sovereign Fixed Maturity and Equity Securities in European Peripheral Region [Line Items]
Available For Sale Securities Amortized Cost	24,449,000	34,459,000
Available For Sale Securities Fair Value Disclosure	$ 24,450,000	$ 33,137,000
Percentage Of Total Available For Sales Securities	35.40%	44.90%

This item represents the cost of debt and equity securities, which are categorized neither as held-to-maturity nor trading, net of adjustments including accretion, amortization, collection of cash, previous other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments recognized, as defined), and fair value hedge accounting adjustments, if any.

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This element represents the portion of the balance sheet assertion valued at fair value by the entity whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission. This item represents Available-for-sale Securities which consist of all investments in certain debt and equity securities neither classified as trading or held-to-maturity securities. A debt security represents a creditor relationship with an enterprise. Debt securities include, among other items, US Treasury securities, US government securities, municipal securities, corporate bonds, convertible debt, commercial paper, and all securitized debt instruments. An equity security represents an ownership interest in an enterprise or the right to acquire or dispose of an ownership interest in an enterprise at fixed or determinable prices. Equity securities include, among other things, common stock, certain preferred stock, warrant rights, call options, and put options, but do not include convertible debt. An entity may opt to provide the reader with additional narrative text to better understand the nature of investments in debt and equity securities which are categorized as Available-for-sale.

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