SCHEDULE I - Consolidated Summary of Investments Other Than Investments in Related Parties (Details) (USD $)	Dec. 31, 2014
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Investments Not Carried At Fair Value	$ 187,000,000
Trading securities [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Fair value	15,112,413,000	[1]
Amount at which shown in the balance sheet	15,112,413,000	[1]
Trading securities [Member] | Fixed maturities
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	13,489,633,000	[1],[2]
Fair value	13,918,745,000	[1]
Amount at which shown in the balance sheet	13,918,745,000	[1]
Trading securities [Member] | Fixed maturities | U.S. government and government sponsored enterprises
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	2,308,264,000	[1],[2]
Fair value	2,315,422,000	[1]
Amount at which shown in the balance sheet	2,315,422,000	[1]
Trading securities [Member] | Fixed maturities | U.S. states, territories and municipalities
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	511,228,000	[1],[2]
Fair value	530,603,000	[1]
Amount at which shown in the balance sheet	530,603,000	[1]
Trading securities [Member] | Fixed maturities | Non-U.S. sovereign government, supranational and government related
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	1,866,915,000	[1],[2]
Fair value	1,976,202,000	[1]
Amount at which shown in the balance sheet	1,976,202,000	[1]
Trading securities [Member] | Fixed maturities | Corporate
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	5,363,006,000	[1],[2]
Fair value	5,604,160,000	[1]
Amount at which shown in the balance sheet	5,604,160,000	[1]
Trading securities [Member] | Fixed maturities | Asset-backed securities
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	1,110,393,000	[1],[2]
Fair value	1,131,420,000	[1]
Amount at which shown in the balance sheet	1,131,420,000	[1]
Trading securities [Member] | Fixed maturities | Residential mortgage-backed securities
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	2,276,200,000	[1],[2]
Fair value	2,306,476,000	[1]
Amount at which shown in the balance sheet	2,306,476,000	[1]
Trading securities [Member] | Fixed maturities | Other mortgage-backed securities
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	53,627,000	[1],[2]
Fair value	54,462,000	[1]
Amount at which shown in the balance sheet	54,462,000	[1]
Trading securities [Member] | Equities
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	843,429,000	[1],[2]
Fair value	1,056,514,000	[1]
Amount at which shown in the balance sheet	1,056,514,000	[1]
Trading securities [Member] | Equities | Banks, trust and insurance companies
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	134,972,000	[1],[2]
Fair value	243,765,000	[1]
Amount at which shown in the balance sheet	243,765,000	[1]
Trading securities [Member] | Equities | Public utilities
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	28,169,000	[1],[2]
Fair value	31,748,000	[1]
Amount at which shown in the balance sheet	31,748,000	[1]
Trading securities [Member] | Equities | Industrial, miscellaneous and all other
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	680,288,000	[1],[2]
Fair value	781,001,000	[1]
Amount at which shown in the balance sheet	781,001,000	[1]
Trading securities [Member] | Short-term investments
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	25,699,000	[1],[2]
Fair value	25,678,000	[1]
Amount at which shown in the balance sheet	25,678,000	[1]
Trading securities [Member] | Other invested assets [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Fair value	111,476,000	[1],[3]
Amount at which shown in the balance sheet	$ 111,476,000	[1],[3]

[1] Excludes the investment portfolio underlying the funds held – directly managed account. While the net investment income and net realized and unrealized gains and losses inure to the benefit of the Company, the Company does not legally own the investments.

[2] Original cost of fixed maturities reduced by repayments and adjusted for amortization of premiums or accrual of discounts. Original cost of equity securities.

[3] Other invested assets excludes the Company’s investments accounted for using the cost method of accounting and the equity method of accounting of $187 million.