Schedule I Summary Of Investments (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Summary of Investments, Other than Investments in Related Parties, Cost	$ 3,549,780
Summary of Investments, Other than Investments in Related Parties, Fair Value	3,635,227
Summary of Investments, Other than Investments in Related Parties, Carrying Amount	3,629,299
US Treasury and Government [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Summary of Investments, Other than Investments in Related Parties, Cost	5,709
Summary of Investments, Other than Investments in Related Parties, Fair Value	5,751
Summary of Investments, Other than Investments in Related Parties, Carrying Amount	5,751
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	17,727	[1]
Summary of Investments, Other than Investments in Related Parties, Fair Value	18,910	[1]
Summary of Investments, Other than Investments in Related Parties, Carrying Amount	18,910	[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	277,678
Summary of Investments, Other than Investments in Related Parties, Fair Value	284,408
Summary of Investments, Other than Investments in Related Parties, Carrying Amount	284,408
RMBS
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Summary of Investments, Other than Investments in Related Parties, Cost	41,467
Summary of Investments, Other than Investments in Related Parties, Fair Value	42,520
Summary of Investments, Other than Investments in Related Parties, Carrying Amount	42,520
CMBS
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Summary of Investments, Other than Investments in Related Parties, Cost	57,358
Summary of Investments, Other than Investments in Related Parties, Fair Value	58,234
Summary of Investments, Other than Investments in Related Parties, Carrying Amount	58,234
Other ABS
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Summary of Investments, Other than Investments in Related Parties, Cost	109,420
Summary of Investments, Other than Investments in Related Parties, Fair Value	107,701
Summary of Investments, Other than Investments in Related Parties, Carrying Amount	107,701
Foreign government securities
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Summary of Investments, Other than Investments in Related Parties, Cost	19,301
Summary of Investments, Other than Investments in Related Parties, Fair Value	19,366
Summary of Investments, Other than Investments in Related Parties, Carrying Amount	19,366
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	528,660
Summary of Investments, Other than Investments in Related Parties, Fair Value	536,890
Summary of Investments, Other than Investments in Related Parties, Carrying Amount	536,890
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	1,628,769	[2]
Summary of Investments, Other than Investments in Related Parties, Fair Value	1,633,584	[2]
Summary of Investments, Other than Investments in Related Parties, Carrying Amount	1,633,584	[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	76,827
Summary of Investments, Other than Investments in Related Parties, Fair Value	142,981
Summary of Investments, Other than Investments in Related Parties, Carrying Amount	142,981
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	73
Summary of Investments, Other than Investments in Related Parties, Fair Value	387
Summary of Investments, Other than Investments in Related Parties, Carrying Amount	387
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	76,900
Summary of Investments, Other than Investments in Related Parties, Fair Value	143,368
Summary of Investments, Other than Investments in Related Parties, Carrying Amount	143,368
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	1,300,866
Summary of Investments, Other than Investments in Related Parties, Fair Value	1,300,872
Summary of Investments, Other than Investments in Related Parties, Carrying Amount	1,300,872
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	14,585
Summary of Investments, Other than Investments in Related Parties, Fair Value	20,513
Summary of Investments, Other than Investments in Related Parties, Carrying Amount	$ 14,585

[1] Available for sale.

[2] Includes foreign government and agency securities.