Schedule I Summary Of Investments (Details) $ in Thousands	Dec. 31, 2015 USD ($)
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Summary of Investments, Other than Investments in Related Parties, Cost	$ 4,348,882
Summary of Investments, Other than Investments in Related Parties, Fair Value	4,301,872
Summary of Investments, Other than Investments in Related Parties, Carrying Amount	4,298,686
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	13,773
Summary of Investments, Other than Investments in Related Parties, Fair Value	13,752
Summary of Investments, Other than Investments in Related Parties, Carrying Amount	13,752
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	36,920	[1]
Summary of Investments, Other than Investments in Related Parties, Fair Value	37,900	[1]
Summary of Investments, Other than Investments in Related Parties, Carrying Amount	37,900	[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	815,024
Summary of Investments, Other than Investments in Related Parties, Fair Value	802,193
Summary of Investments, Other than Investments in Related Parties, Carrying Amount	802,193
RMBS
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Summary of Investments, Other than Investments in Related Parties, Cost	226,744
Summary of Investments, Other than Investments in Related Parties, Fair Value	224,905
Summary of Investments, Other than Investments in Related Parties, Carrying Amount	224,905
CMBS
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Summary of Investments, Other than Investments in Related Parties, Cost	415,780
Summary of Investments, Other than Investments in Related Parties, Fair Value	406,910
Summary of Investments, Other than Investments in Related Parties, Carrying Amount	406,910
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	359,452
Summary of Investments, Other than Investments in Related Parties, Fair Value	355,494
Summary of Investments, Other than Investments in Related Parties, Carrying Amount	355,494
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	25,663
Summary of Investments, Other than Investments in Related Parties, Fair Value	24,307
Summary of Investments, Other than Investments in Related Parties, Carrying Amount	24,307
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	1,893,356
Summary of Investments, Other than Investments in Related Parties, Fair Value	1,865,461
Summary of Investments, Other than Investments in Related Parties, Carrying Amount	1,865,461
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	1,301,187	[2]
Summary of Investments, Other than Investments in Related Parties, Fair Value	1,279,137	[2]
Summary of Investments, Other than Investments in Related Parties, Carrying Amount	1,279,137	[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	75,038
Summary of Investments, Other than Investments in Related Parties, Fair Value	74,930
Summary of Investments, Other than Investments in Related Parties, Carrying Amount	74,930
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	500
Summary of Investments, Other than Investments in Related Parties, Fair Value	500
Summary of Investments, Other than Investments in Related Parties, Carrying Amount	500
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	75,538
Summary of Investments, Other than Investments in Related Parties, Fair Value	75,430
Summary of Investments, Other than Investments in Related Parties, Carrying Amount	75,430
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	1,077,087
Summary of Investments, Other than Investments in Related Parties, Fair Value	1,076,944
Summary of Investments, Other than Investments in Related Parties, Carrying Amount	1,076,944
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	1,714
Summary of Investments, Other than Investments in Related Parties, Fair Value	4,900
Summary of Investments, Other than Investments in Related Parties, Carrying Amount	$ 1,714

[1] Available for sale.

[2] Includes foreign government and agency securities.