Schedule I Summary Of Investments (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Summary of Investments, Other than Investments in Related Parties, Cost	$ 5,009,552
Summary of Investments, Other than Investments in Related Parties, Fair Value	4,938,046
Summary of Investments, Other than Investments in Related Parties, Carrying Amount	4,931,157
US Government and Government Agencies and Authorities [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Summary of Investments, Other than Investments in Related Parties, Cost	8,939
Summary of Investments, Other than Investments in Related Parties, Fair Value	9,106
Summary of Investments, Other than Investments in Related Parties, Carrying Amount	9,106
US States and Political Subdivisions Debt Securities [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Summary of Investments, Other than Investments in Related Parties, Cost	26,847	[1]
Summary of Investments, Other than Investments in Related Parties, Fair Value	26,296	[1]
Summary of Investments, Other than Investments in Related Parties, Carrying Amount	26,304	[1]
All Other Corporate Bonds [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Summary of Investments, Other than Investments in Related Parties, Cost	11,951
Summary of Investments, Other than Investments in Related Parties, Fair Value	12,045
Summary of Investments, Other than Investments in Related Parties, Carrying Amount	12,045
Residential Mortgage Backed Securities [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Summary of Investments, Other than Investments in Related Parties, Cost	72,665
Summary of Investments, Other than Investments in Related Parties, Fair Value	73,115
Summary of Investments, Other than Investments in Related Parties, Carrying Amount	73,115
Other investments
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Summary of Investments, Other than Investments in Related Parties, Cost	341
Summary of Investments, Other than Investments in Related Parties, Fair Value	341
Summary of Investments, Other than Investments in Related Parties, Carrying Amount	341
Fixed Maturities [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Summary of Investments, Other than Investments in Related Parties, Cost	120,743
Summary of Investments, Other than Investments in Related Parties, Fair Value	120,903
Summary of Investments, Other than Investments in Related Parties, Carrying Amount	120,911
Trading Assets, Excluding Debt and Equity Securities [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Summary of Investments, Other than Investments in Related Parties, Cost	3,255,921	[2]
Summary of Investments, Other than Investments in Related Parties, Fair Value	3,117,429	[2]
Summary of Investments, Other than Investments in Related Parties, Carrying Amount	3,117,429	[2]
Common Stocks, by Industry [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Summary of Investments, Other than Investments in Related Parties, Cost	77,758
Summary of Investments, Other than Investments in Related Parties, Fair Value	129,939
Summary of Investments, Other than Investments in Related Parties, Carrying Amount	129,939
Nonredeemable Preferred Stock [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Summary of Investments, Other than Investments in Related Parties, Cost	348
Summary of Investments, Other than Investments in Related Parties, Fair Value	5,229
Summary of Investments, Other than Investments in Related Parties, Carrying Amount	5,229
Equity Securities, Investment Summary [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Summary of Investments, Other than Investments in Related Parties, Cost	78,106
Summary of Investments, Other than Investments in Related Parties, Fair Value	135,168
Summary of Investments, Other than Investments in Related Parties, Carrying Amount	135,168
Short-term Investments [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Summary of Investments, Other than Investments in Related Parties, Cost	1,429,227
Summary of Investments, Other than Investments in Related Parties, Fair Value	1,429,228
Summary of Investments, Other than Investments in Related Parties, Carrying Amount	1,429,228
Other Long-term Investments [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Summary of Investments, Other than Investments in Related Parties, Cost	125,555
Summary of Investments, Other than Investments in Related Parties, Fair Value	135,318
Summary of Investments, Other than Investments in Related Parties, Carrying Amount	$ 128,421

[1] Held to maturity and available for sale.

[2] Includes foreign government and agency securities.