Schedule I Summary Of Investments (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Summary of Investments, Other than Investments in Related Parties, Cost	$ 5,661,888
Summary of Investments, Other than Investments in Related Parties, Fair Value	5,785,502
Summary of Investments, Other than Investments in Related Parties, Carrying Amount	5,783,559
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	10,931
Summary of Investments, Other than Investments in Related Parties, Fair Value	13,630
Summary of Investments, Other than Investments in Related Parties, Carrying Amount	13,630
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	89,723	[1]
Summary of Investments, Other than Investments in Related Parties, Fair Value	85,440	[1]
Summary of Investments, Other than Investments in Related Parties, Carrying Amount	85,332	[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	17,267
Summary of Investments, Other than Investments in Related Parties, Fair Value	16,610
Summary of Investments, Other than Investments in Related Parties, Carrying Amount	16,610
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	1,308
Summary of Investments, Other than Investments in Related Parties, Fair Value	1,360
Summary of Investments, Other than Investments in Related Parties, Carrying Amount	1,360
Commercial 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	1,660
Summary of Investments, Other than Investments in Related Parties, Fair Value	1,669
Summary of Investments, Other than Investments in Related Parties, Carrying Amount	1,669
Asset-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	1,019
Summary of Investments, Other than Investments in Related Parties, Fair Value	1,177
Summary of Investments, Other than Investments in Related Parties, Carrying Amount	1,177
Other 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	1,489
Summary of Investments, Other than Investments in Related Parties, Fair Value	1,595
Summary of Investments, Other than Investments in Related Parties, Carrying Amount	1,595
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	123,397
Summary of Investments, Other than Investments in Related Parties, Fair Value	121,481
Summary of Investments, Other than Investments in Related Parties, Carrying Amount	121,373
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	4,101,355
Summary of Investments, Other than Investments in Related Parties, Fair Value	4,211,059
Summary of Investments, Other than Investments in Related Parties, Carrying Amount	4,211,059
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	103,923
Summary of Investments, Other than Investments in Related Parties, Fair Value	118,354
Summary of Investments, Other than Investments in Related Parties, Carrying Amount	118,354
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	10,502
Summary of Investments, Other than Investments in Related Parties, Fair Value	10,070
Summary of Investments, Other than Investments in Related Parties, Carrying Amount	10,070
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	114,425
Summary of Investments, Other than Investments in Related Parties, Fair Value	128,424
Summary of Investments, Other than Investments in Related Parties, Carrying Amount	128,424
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	1,261,711
Summary of Investments, Other than Investments in Related Parties, Fair Value	1,261,703
Summary of Investments, Other than Investments in Related Parties, Carrying Amount	1,261,703
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	61,000
Summary of Investments, Other than Investments in Related Parties, Fair Value	62,835
Summary of Investments, Other than Investments in Related Parties, Carrying Amount	$ 61,000

[1] Held to maturity and available for sale.